Gavin Lotay

Dr Gavin Lotay


Reader, Director of Learning and Teaching for Physics
+44 (0)1483 689589
22 BC 04

Academic and research departments

Department of Physics.

Biography

Areas of specialism

Nuclear Astrophysics; Gamma-ray Spectroscopy; Transfer Reactions; Direct Measurements

University roles and responsibilities

  • Director of Learning and Teaching

    Research

    Research interests

    My teaching

    My publications

    Publications

    A Kankainen, PJ Woods, H Schatz, T Poxon-Pearson, Daniel Doherty, V Bader, T Baugher, D Bazin, BA Brown, J Browne, A Estrade, A Gade, J José, A Kontos, C Langer, Gavin Lotay, Z Meisel, F Montes, S Noji, F Nunes, G Perdikakis, J Pereira, F Recchia, T Redpath, R Stroberg, M Scott, D Seweryniak, J Stevens, D Weisshaar, R Zegers (2017)Measurement of key resonance states for the 30P(p, γ)31Sreaction rate, and the production of intermediate-mass elements in nova explosions, In: Physics Letters B769pp. 549-553 Elsevier

    We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the 30P(p, γ)31Sreaction critical for determining the production of intermediate-mass elements up to Ca in nova ejecta. The 30P(d, n)31Sreaction was studied in inverse kinematics using the GRETINA γ-ray array to measure the angle-integrated cross-sections of states above the proton threshold. In general, negative-parity states are found to be most strongly produced but the absolute values of spectroscopic factors are typically an order of magnitude lower than predicted by the shell-model calculations employing WBP Hamiltonian for the negative-parity states. The results clearly indicate the dominance of a single 3/2−resonance state at 196 keV in the region of nova burning T≈0.10–0.17GK, well within the region of interest for nova nucleosynthesis. Hydrodynamic simulations of nova explosions have been performed to demonstrate the effect on the composition of nova ejecta.

    S. Ota, G. Christian, G. Lotay, W.N Catford, E.A Bennett, S. Dede, Daniel Doherty, Sam Hallam, J. Hooker, C. Hunt, H. Jayatissa, A. Matta, Mohamad Moukaddam, G.V Rogachev, A. Saastamoinen, Jeffrey Tostevin, S. Upadhyayula, Ryan Wilkinson (2020)Decay properties of 22Ne + resonances and their impact on s-process nucleosynthesis, In: Physics Letters B802135256 Elsevier

    The astrophysical s-process is one of the two main processes forming elements heavier than iron. A key outstanding uncertainty surrounding s-process nucleosynthesis is the neutron flux generated by the 22Ne(; n)25Mg reaction during the He-core and C-shell burning phases of massive stars. This reaction, as well as the competing 22Ne(;)26Mg reaction, is not well constrained in the important temperature regime from 0:2–0:4 GK, owing to uncertainties in the nuclear properties of resonances lying within the Gamow window. To address these uncertainties, we have performed a new measurement of the 22Ne(6Li; d)26Mg reaction in inverse kinematics, detecting the outgoing deuterons and 25;26Mg recoils in coincidence. We have established a new n= decay branching ratio of 1:14(26) for the key Ex = 11:32 MeV resonance in 26Mg, which results in a new (; n) strength for this resonance of 42(11) eV when combined with the well-established (; ) strength of this resonance. We have also determined new upper limits on the partial widths of neutron-unbound resonances at Ex = 11:112; 11:163, 11:169, and 11:171 MeV. Monte-Carlo calculations of the stellar 22Ne(; n)25Mg and 22Ne(; )26Mg rates, which incorporate these results, indicate that both rates are substantially lower than previously thought in the temperature range from 0:2–0:4 GK.

    S Hallam, G Lotay, A Gade, D T Doherty, J Belarge, P C Bender, B A Brown, J Browne, W N Catford, B Elman, A Estradé, M R Hall, B Longfellow, E Lunderberg, F Montes, M Moukaddam, P O'Malley, W-J Ong, H Schatz, D Seweryniak, K Schmidt, N K Timofeyuk, D Weisshaar, R G T Zegers (2021)Exploiting Isospin Symmetry to Study the Role of Isomers in Stellar Environments, In: Physical review letters126(4)042701 American Physical Society

    Proton capture on the excited isomeric state of ^{26}Al strongly influences the abundance of ^{26}Mg ejected in explosive astronomical events and, as such, plays a critical role in determining the initial content of radiogenic ^{26}Al in presolar grains. This reaction also affects the temperature range for thermal equilibrium between the ground and isomeric levels. We present a novel technique, which exploits the isospin symmetry of the nuclear force, to address the long-standing challenge of determining proton-capture rates on excited nuclear levels. Such a technique has in-built tests that strongly support its veracity and, for the first time, we have experimentally constrained the strengths of resonances that dominate the astrophysical ^{26m}Al(p,γ)^{27}Si reaction. These constraints demonstrate that the rate is at least a factor ∼8 lower than previously expected, indicating an increase in the stellar production of ^{26}Mg and a possible need to reinvestigate sensitivity studies involving the thermal equilibration of ^{26}Al.

    A. R. L Kennington, G Lotay, D. T Doherty, D Seweryniak, C Andreoiu, K Auranen, M. P Carpenter, W. N Catford, C. M Deibel, K Hadyńska-Klȩk, S Hallam, D Hoff, T Huang, R. V. F Janssens, S Jazrawi, J José, F. G Kondev, T Lauritsen, J Li, A. M Rogers, J Saiz, G Savard, S Stolze, G. L Wilson, S Zhu (2021)Level structure of the Tz=−1 nucleus Ar34 and its relevance for nucleosynthesis in ONe novae, In: Physical review. C103(3)035805 American Physical Society

    The 24 Mg + 12 C fusion reaction was used to perform a detailed γ-ray spectroscopy study of the astrophysically important nucleus 34 Ar. In particular, an experimental setup, coupling the advanced γ-ray tracking array GRETINA with the well-established Argonne fragment mass analyzer (FMA), was employed to obtain excitation energies and spin-parity assignments for excited states in 34 Ar, both above and below the proton separation energy. For the first time, an angular distribution analysis of in-beam γ rays from fusion-evaporation reactions, using a tracking array, has been performed and Coulomb energy differences of analog states in the T = 1, A = 34 mirror system, explored from 0 to 6 MeV. Furthermore, we present a comprehensive discussion of the astrophysical 33 Cl(p, γ) stellar reaction rate, together with implications for the identification of nova presolar grains from sulfur isotopic abundances.

    GAVIN JAMES LOTAY, P.J. Woods, M Moukaddam, M Aliotta, G Christian, B Davids, T Davinson, D.T. Doherty, D. Howell, V. Margerin, C. Ruiz (2020)High-resolution radioactive beam study of the 26Al(d,p) reaction and measurements of single-particle spectroscopic factors, In: The European Physical Journal. A, Hadrons and nuclei56(3) Springer Nature B.V

    We present a detailed comparison of shell model calculations with inverse kinematic transfer reaction data, obtained using a radioactive beam. Experimentally extracted spectroscopic factors from the 26Al(d,p)27Al reaction for both even and odd parity states are found to be exceptionally well reproduced by the shell model and a high level of consistency is observed between bound isobaric analog states in 27Al and 27Si, populated via (d, p) and (d, n) transfer, respectively. Furthermore, an evaluation of key resonances in the astrophysical 26Al(p,γ)27Si reaction indicates that shell model calculations provide relatively accurate predictions for the existence of strong resonances and mirror nucleus comparisons appear to hold exceptionally well for proton-unbound levels. Consequently, we expect that the utilization of both techniques will likely be a very effective tool in the investigation of stellar processes outside the current reach of experiment.

    H Watanabe, G Zhang, K Yoshida, Philip Walker, J Liu, J Wu, Patrick Regan, PA Soderstrom, H Kanaoka, Z Korkulu, PS Lee, S Nishimura, A Yagi, DS Ahn, T Alharbi, H Baba, F Browne, AM Bruce, RJ Fukuda, C Griffin, E Ideguchi, N Inabe, T Isobe, S Kanaya, I Kojouharov, FG Kondev, T Kubo, S Kubono, N Kurz, I Kuti, S Lalkovski, GJ Lane;, CS Lee, EJ Lee, G Lorusso, Gavin Lotay, CB Moon, I Nishizuka, CR Nita, A Odahara, Z Patel, VH Phong, Zsolt Podolyak, OJ Roberts, H Sakurai, H Schaffner, Callum Shand, Y Shimizu, T Sumikama, H Suzuki, H Takeda, S Terashima, Z Vajta;, JJ Valiente-Dobon, ZY Xu (2016)Long-lived K isomer and enhanced gamma vibration in the neutron-rich nucleus 172Dy: Collectivity beyond double midshell, In: Physics Letters B760(Sept)pp. 641-646 Elsevier

    The level structure of 172Dy has been investigated for the first time by means of decay spectroscopy following in-flight fission of a 238U beam. A long-lived isomeric state with T1/2 = 0.71(5) s and K π = 8 − has been identified at 1278 keV, which decays to the ground-state and γ-vibrational bands through hindered electromagnetic transitions, as well as to the daughter nucleus 172Ho via allowed β decays. The robust nature of the K π = 8 − isomer and the ground-state rotational band reveals an axially-symmetric structure for this nucleus. Meanwhile, the γ-vibrational levels have been identified at unusually low excitation energy compared to the neighboring well-deformed nuclei, indicating the significance of the microscopic effect on the non-axial collectivity in this doubly mid-shell region. The underlying mechanism of enhanced γ vibration is discussed in comparison with the deformed Quasiparticle Random-Phase Approximation based on a Skyrme energy-density functional.

    P.-A. Söderström, Philip Walker, J. Wu, H. L. Liu, Patrick Regan, H. Watanabe, P. Doornenbal, Z. Korkulu, P. Lee, J. J. Liu, G. Lorusso, S. Nishimura, V. H. Phong, T. Sumikama, F. R. Xu, A. Yagi, G. X. Zhang, D. S. Ahn, T. Alharbi, H. Baba, F. Browne, A. M. Bruce, R. J. Carroll, K. Y. Chae, Zs. Dombradi, A. Estrade, N. Fukuda, C. Griffin, E. Ideguchi, N Inabe, T. Isobe, H. Kanaoka, S. Kanaya, I. Kojouharov, F. G. Kondev, T. Kubo, S. Kubono, N. Kurz, I. Kuti, S. Lalkovski, G. J. Lane, E. J. Lee, C. S. Lee, GAVIN JAMES LOTAY, C.-B. Moon, I. Nishizuka, C. R. Nita, A. Odahara, Z. Patel, Zsolt Podolyak, O. J. Roberts, H. Sakurai, H. Schaffner, C. M. Shand, H. Suzuki, H. Takeda, S. Terashima, Zs. Vajta, J. J. Valiente-Dòbon, Z. Y. Xui (2016)Collective And Single-particle Structures In The Neutron-rich Doubly Mid-shell Nucleus 170Dy, In: Proceedings of Science: The 26th International Nuclear Physics Conference

    One of the most successful descriptions of the structure of atomic nuclei is the spherical shell model. It, however, becomes impractical when moving away from closed-shell nuclei. Instead, it is the interplay between the macroscopic shape degrees of freedom and the microscopic nature of the underlying single-particle structure in a deformed basis that determines the nuclear structure. Being the heaviest nucleus precisely in the middle of, known, closed proton and neutron shells, 170Dy has become a central calibration point for tests of collective models of nuclear physics. However, besides one candidate transition from a previous experiment in Legnaro, Italy, no experimental information is available for this nucleus. Using the EURICA setup at RIKEN, which couples the worlds highest intensity in-flight fission facility with a high-efficiency HPGe array, an experiment in November 2014 produced 170Dy nuclei by in-flight fission of a 238U beam. The results from this experiment provide a wealth of information on this elusive nucleus, including the evolution of quadrupole collectivity, rigidity and higher order deformations, as well as the long sought for isomeric K = 6+ state, predicted to be exceptionally pure at mid-shell. These results provide us with a rich level scheme for discussing both single-particle and collective structures at mid-shell.

    Laila Gurgi, Patrick Regan, P-A Söderström, H Watanabe, Philip Walker, Zsolt Podolyak, S Nishimura, Thomas Berry, P Doornenbal, G Lorusso, T Isobe, H Baba, ZY Xu, H Sakurai, T Sumikama, Wilton Catford, AM Bruce, F Browne, GJ Lane, FG Kondev, A Odahara, J Wu, HL Liu, FR Xu, Z Korkulu, P Lee, JJ Liu, VH Phong, A Yag, GX Zhang, T Alharbi, RJ Carroll, KY Chae, Zs Dombradi, A Estrade, N Fukuda, C Griffin, E Ideguchi, N Inabe, H Kanaoka, I Kojouharov, T Kubo, S Kubono, N Kurz, I Kuti, S Lalkovski, EJ Lee, CS Lee, Gavin Lotay, C-B Moon, I Nishizuka, CR Nita, Z Patel, OJ Roberts, H Schaffner, Callum Shand, H Suzuki, H Takeda, S Terashima, Zs Vajta, S Yoshida, JJ Valiente-Dòbon (2016)Isomer spectroscopy of neutron-rich 168Tb103, In: Radiation Physics and Chemistry140pp. 493-496 Elsevier

    In-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm thick 9Be target has been used to produce and study the decays of a range of neutron-rich nuclei centred around the doubly mid-shell nucleus 170Dy at the RIBF Facility, RIKEN, Japan. The produced secondary fragments of interest were identified eventby- event using the BigRIPS separator. The fragments were implanted into the WAS3ABI position sensitive silicon active stopper which allowed pixelated correlations between implants and their subsequent β-decay. Discrete γ-ray transitions emitted following decays from either metastable states or excited states populated following beta decay were identified using the 84 coaxial high-purity germanium (HPGe) detectors of the EURICA spectrometer, which was complemented by 18 additional cerium-doped lanthanum bromide (LaBr3)

    G Lotay, PJ Woods, D Seweryniak, MP Carpenter, N Hoteling, RVF Janssens, DG Jenkins, T Lauritsen, CJ Lister, A Robinson, S Zhu (2008)First in-beam γ-ray spectroscopy study of Al24 and its implications for the astrophysical Mg23(p,γ)Al24 reaction rate in ONe novae, In: Physical Review C - Nuclear Physics77(4)

    The first in-beam γ-ray spectroscopy study of Al24 is presented. A complete level structure of Al24 incorporating all states below the proton-emission threshold, has been constructed. The first excited state above the proton threshold has also been identified as a 3+ state at 2345.1 ± 1.4 keV. This state, corresponding to a resonance energy of 473 ± 3 keV, has been suggested to be the dominant resonance contributing to the Mg23(p,γ)Al24 stellar reaction rate. The improved precision of the level energy and unambiguous assignment of the state has reduced the uncertainty of the Mg23(p,γ)Al24 stellar reaction rate, which constrains the production of A>20 nuclei in ONe novae. © 2008 The American Physical Society.

    V Margerin, G Lotay, PJ Woods, M Aliotta, G Christian, B Davids, T Davinson, DT Doherty, J Fallis, D Howell, OS Kirsebom, DJ Mountford, A Rojas, C Ruiz, JA Tostevin (2015)Inverse Kinematic Study of the Al26g(d,p)Al27 Reaction and Implications for Destruction of Al26 in Wolf-Rayet and Asymptotic Giant Branch Stars, In: Physical Review Letters115062701 American Physical Society

    In Wolf-Rayet and asymptotic giant branch (AGB) stars, the Al26g(p,γ)Si27 reaction is expected to govern the destruction of the cosmic γ-ray emitting nucleus Al26. The rate of this reaction, however, is highly uncertain due to the unknown properties of key resonances in the temperature regime of hydrogen burning. We present a high-resolution inverse kinematic study of the Al26g(d,p)Al27 reaction as a method for constraining the strengths of key astrophysical resonances in the Al26g(p,γ)Si27 reaction. In particular, the results indicate that the resonance at Er=127  keV in Si27 determines the entire Al26g(p,γ)Si27 reaction rate over almost the complete temperature range of Wolf-Rayet stars and AGB stars.

    M. Rudigier, P. M. Walker, R.L. Canavan, Zs. Podolyak, P. H. Regan, P.-A. Söderström, M. Lebois, J.N. Wilson, N. Jovancevic, A. Blazhev, J. Benito, S. Bottoni, M. Brunet, N. Cieplicka-Orynczak, S. Courtin, D. T. Doherty, L.M. Fraile, K. Hadynska-Klek, M. Heine, Ł.W. Iskra, J. Jolie, V. Karayonchev, A. R. Kennington, P. Koseoglou, G. Lotay, G. Lorusso, M. Nakhostin, C.R. Nita, S. Oberstedt, L. Qi, J.-M. Régis, V. Sánchez-Tembleque, R. Shearman, W. Witt, V. Vedia, K.O. Zell (2020)Multi-quasiparticle sub-nanosecond isomers in 178W, In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics801135140 Elsevier

    We report on the first measurement of the half-lives of and four-quasiparticle states in the even-even nucleus 178W. The sub-nanosecond half-lives were measured by applying the centroid shift method to data taken with LaBr3(Ce) scintillator detectors of the NuBall array at the ALTO facility in Orsay, France. The half-lives of these states only became experimentally accessible by the combination of several experimental techniques - scintillator fast timing, isomer spectroscopy with a pulsed beam, and the event-by-event calorimetry information provided by the NuBall array. The measured half-lives are and for the and states, respectively. The decay transitions include weakly hindered E1 and E2 branches directly to the ground-state band, bypassing the two-quasiparticle states. This is the first such observation for an E1 transition. The interpretation of the small hindrance hinges on mixing between the ground-state band and the t-band.

    A Kankainen, PJ Woods, F Nunes, C Langer, H Schatz, V Bader, T Baugher, D Bazin, BA Brown, J Browne, DT Doherty, A Estrade, A Gade, A Kontos, G Lotay, Z Meisel, F Montes, S Noji, G Perdikakis, J Pereira, F Recchia, T Redpath, R Stroberg, M Scott, D Seweryniak, J Stevens, D Weisshaar, K Wimmer, R Zegers (2016)Angle-integrated measurements of the Al-26(d, n)Si-27 reaction cross section: a probe of spectroscopic factors and astrophysical resonance strengths, In: EUROPEAN PHYSICAL JOURNAL A52(1)ARTN 6 SPRINGER
    G Lotay, PJ Woods, D Seweryniak, MP Carpenter, HM David, RVF Janssens, S Zhu (2011)Identification of analog states in the T=1/2 A=27 mirror system from low excitation energies to the region of hydrogen burning in the 26Alg ,m(p,γ)27Si reactions, In: Physical Review C - Nuclear Physics84(3)

    The reactions 26Alg(p,γ)27Si and 26Alm(p,γ)27Si are important for influencing the galactic abundance of the cosmic γ-ray emitter 26Alg and for the excess abundance of 26Mg found in presolar grains, respectively. Precise excitation energies and spin assignments of states from the ground state to the region of astrophysical interest in 27Si, including the identification and pairing of key astrophysical resonances with analog states in the mirror nucleus 27Al, are reported using γ rays observed in the 12C + 16O fusion reaction. The detailed evolution of Coulomb energy differences between the states in 27Si and 27Al is explored, including the region above the astrophysical reaction thresholds. © 2011 American Physical Society.

    M Assié, FDO Santos, T Davinson, FD Grancey, L Achouri, J Alcántara-Núñez, TA Kalanee, J-C Angélique, C Borcea, R Borcea, L Caceres, I Celikovic, V Chudoba, DY Pang, C Ducoin, M Fallot, O Kamalou, J Kiener, Y Lam, A Lefebvre-Schuhl, G Lotay, J Mrazek, L Perrot, AM Sánchez-Benítez, F Rotaru, M-G Saint-Laurent, Y Sobolev, N Smirnova, M Stanoiu, I Stefan, K Subotic, P Ujic, R Wolski, PJ Woods (2011)Spectroscopy of $^{18}$Na: Bridging the two-proton radioactivity of $^{19}$Mg

    The unbound nucleus $^{18}$Na, the intermediate nucleus in the two-proton radioactivity of $^{19}$Mg, was studied by the measurement of the resonant elastic scattering reaction $^{17}$Ne(p,$^{17}$Ne)p performed at 4 A.MeV. Spectroscopic properties of the low-lying states were obtained in a R-matrix analysis of the excitation function. Using these new results, we show that the lifetime of the $^{19}$Mg radioactivity can be understood assuming a sequential emission of two protons via low energy tails of $^{18}$Na resonances.

    NS Pattabiraman, DG Jenkins, MA Bentley, R Wadsworth, CJ Lister, MP Carpenter, RVF Janssens, TL Khoo, T Lauritsen, D Seweryniak, S Zhu, G Lotay, PJ Woods, PV Krishichayan, Isacker (2008)Analog E1 transitions and isospin mixing, In: Physical Review C - Nuclear Physics78(2)

    We investigate whether isospin mixing can be determined in a model-independent way from the relative strength of E1 transitions in mirror nuclei. The specific examples considered are the A=31 and A=35 mirror pairs, where a serious discrepancy between the strengths of 7/2-→5/2+ transitions in the respective mirror nuclei has been observed. A theoretical analysis of the problem suggests that it ought to be possible to disentangle the isospin mixing in the initial and final states given sufficient information on experimental matrix elements. With this in mind, we obtain a lifetime for the relevant 7/2- state in S31 using the Doppler-shift attenuation method. We then collate the available information on matrix elements to examine the level of isospin mixing for both A=31 and A=35 mirror pairs. © 2008 The American Physical Society.

    JP Wallace, G Lotay, PJ Woods, A Alharbi, A Banu, HM David, T Davinson, M McCleskey, B Roeder, E Simmons, A Spiridon, R Tribble, L Trache (2010)Measurement of the β-p emission of 20Mg and the breakout from the hot CNO cycle, In: AIP Conference Proceedings1304pp. 429-431

    In the astrophysically important reaction 19Ne(p,γ) 20Na, the rate is dominated by a single key resonance at 450 keV above the proton-emission threshold in 20Na. Throughout the last few decades many experiments have been performed aimed at finding the identity of this state. Despite this, the spin-parity of the key resonant state is still up for debate. The present paper describes a new experiment studying the β-delayed proton decay of 20Mg aimed at solving this issue. © 2010 American Institute of Physics.

    PJ Salter, M Aliotta, T Davinson, H Al Falou, A Chen, B Davids, BR Fulton, N Galinski, D Howell, G Lotay, P Machule, AS Murphy, C Ruiz, S Sjue, M Taggart, P Walden, PJ Woods (2012)Measurement of the 18Ne(α,p0) 21Na reaction cross section in the burning energy region for x-ray bursts., In: Phys Rev Lett108(24)pp. 242701-?

    The 18Ne(α,p) 21Na reaction provides one of the main HCNO-breakout routes into the rp process in x-ray bursts. The 18Ne(α,p0) 21Na reaction cross section has been determined for the first time in the Gamow energy region for peak temperatures T∼2  GK by measuring its time-reversal reaction 21Na(p,α) 18Ne in inverse kinematics. The astrophysical rate for ground-state to ground-state transitions was found to be a factor of 2 lower than Hauser-Feshbach theoretical predictions. Our reduced rate will affect the physical conditions under which breakout from the HCNO cycles occurs via the 18Ne(α,p) 21Na reaction.

    DT Doherty, G Lotay, PJ Woods, D Seweryniak, MP Carpenter, CJ Chiara, HM David, RV Janssens, L Trache, S Zhu (2012)Key resonances in the 30P(p,γ)31S gateway reaction for the production of heavy elements in ONe novae., In: Phys Rev Lett108(26)pp. 262502-?

    Material emitted as ejecta from ONe novae outbursts is observed to be rich in elements as heavy as Ca. The bottleneck for the synthesis of elements beyond sulphur is the (30)P(p,γ)(31)S reaction. Its reaction rate is, however, not well determined due to uncertainties in the properties of key resonances in the burning regime. In the present study, gamma-ray transitions are reported for the first time from all key states in (31)S relevant for the (30)P(p,γ)(31)S reaction. The spins and parity of these resonances have been deduced, and energies have been measured with the highest precision to date. The uncertainty in the estimated (30)P(p,γ)(31)S reaction rate has been drastically reduced. The rate using this new information is typically higher than previous estimates based on earlier experimental data, implying a higher flux of material processed to high-Z elements in novae, but it is in good agreement with predictions using the Hauser-Feshbach approach at higher burning temperatures.

    G Lotay, PJ Woods, D Seweryniak, MP Carpenter, RVF Janssens, S Zhu (2009)γ-ray spectroscopy study of states in Si27 relevant for the Al26m(p,γ)Si27 reaction in novae and supernovae, In: Physical Review C - Nuclear Physics80(5)

    The heavy-ion, fusion-evaporation reaction C12(O16,n) was used to identify γ-decay transitions from excited states in Si27 above the proton threshold. The precise level energy measurements, Jπ assignments, and lifetime measurements of astrophysically important Al26m+p resonances have allowed an evaluation of the Al26m(p,γ)Si27 reaction rate. An lp=0 resonance has been newly identified at a center-of-mass energy in the Al26m+p system of 146.3(3) keV and is expected to dominate the rate for low stellar temperatures. In addition, an lp=1 resonance has been identified at 378.3(30) keV and is likely to dominate the rate at high astrophysical temperatures, such as those found in oxygen-neon novae and core-collapse supernovae. © 2009 The American Physical Society.

    JP Wallace, PJ Woods, G Lotay, A Alharbi, A Banu, HM David, T Davinson, M McCleskey, BT Roeder, E Simmons, A Spiridon, L Trache, RE Tribble (2012)β-Delayed proton-decay study of 20Mg and its implications for the Ne19(p,γ)Na20 breakout reaction in X-ray bursts, In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics712(1-2)pp. 59-62

    Under astrophysical conditions of high temperature and density, such as for example found in X-ray bursts, breakout can occur from the hot CNO cycles into the rapid proton capture process. A key breakout route is via the sequence O15(α,γ)Ne19(p,γ)Na20. The Ne19(p,γ)Na20 reaction rate is expected to be dominated by a single resonance at 457(3) keV. The identity of the resonance has been under discussion for a long time, with J π=1 + and 3 + assignments suggested. In this study of the β-delayed proton decay of 20Mg we report a new, significantly more stringent, upper limit on the β-decay branch to this state of 0.02% with a confidence level of 90%. This makes a 1 + assignment highly unlikely and favours a 3 + assignment for which no branch is expected to be observed. The 3 + state is predicted to have a significantly higher resonance strength, and to produce a proportionately higher Ne19(p,γ)Na20 reaction rate in X-ray burst conditions. © 2012 Elsevier B.V.

    G Lotay, PJ Woods, D Seweryniak, MP Carpenter, RV Janssens, S Zhu (2009)Identification of key astrophysical resonances relevant for the 26g Al(p,gamma)27Si reaction in Wolf-Rayet stars, AGB stars, and classical novae., In: Phys Rev Lett102(16)pp. 162502-?

    A gamma-ray spectroscopy study of ;{26g}Al+p resonant states in 27Si is presented. Excitation energies were measured with improved precision and first spin-parity assignments made for excited states in 27Si above the proton threshold. The results indicate the presence of low-lying resonances with l_{p}=0 and l_{p}=2 captures that could strongly influence the ;{26g}Al(p,gamma)27Si reaction rate at low stellar temperatures, found in low-mass asymptotic giant branch (AGB), intermediate-mass AGB, super AGB, and Wolf-Rayet stars.

    G. Fruet, S. Courtin, M. Heine, D. G. Jenkins, P. Adsley, A. Brown, R. Canavan, W. N. Catford, E. Charon, D. Curien, S. Della Negra, J. Duprat, F. Hammache, J. Lesrel, G. Lotay, A. Meyer, D. Montanari, L. Morris, M. Moukaddam, J. Nippert, Zs. Podolyak, P. H. Regan, I. Ribaud, M. Richer, M. Rudigier, R. Shearman, N. de Séréville, C. Stodel (2020)Advances in the Direct Study of Carbon Burning in Massive Stars, In: Physical Review Letters124192701 American Physical Society

    The 12C + 12C fusion reaction plays a critical role in the evolution of massive stars and also strongly impacts various explosive astrophysical scenarios. The presence of resonances in this reaction at energies around and below the Coulomb barrier makes it impossible to carry out a simple extrapolation down to the Gamow window—the energy regime relevant to carbon burning in massive stars. The 12C + 12C system forms a unique laboratory for challenging the contemporary picture of deep sub-barrier fusion (possible sub-barrier hindrance) and its interplay with nuclear structure (sub-barrier resonances). Here, we show that direct measurements of the 12C + 12C fusion cross section may be made into the Gamow window using an advanced particle-gamma coincidence technique. The sensitivity of this technique effectively removes ambiguities in existing measurements made with gamma ray or charged-particle detection alone. The present cross-section data span over 8 orders of magnitude and support the fusion-hindrance model at deep sub-barrier energies.

    D Seweryniak, MP Carpenter, S Gros, AA Hecht, N Hoteling, RVF Janssens, TL Khoo, T Lauritsen, CJ Lister, G Lotay, D Peterson, AP Robinson, WB Walters, X Wang, PJ Woods, S Zhu (2009)New results near 100Sn: Observation of single-neutron states in 101Sn, In: Acta Physica Polonica B40(3)pp. 621-627

    A search for in-beam γ-ray transitions in 101Sn, which contains only one neutron outside the 100Sn core, using a novel approach was carried out at the Argonne Tandem-Linac System. 101Sn nuclei were produced using the 46Ti(58Ni, 3n) 101Sn fusion-evaporation reaction. Beta-delayed protons with energies and decay times consistent with previous 101Sn decay studies were observed at the focal plane of the Fragment Mass Analyzer. In-beam γ rays were detected in the Gammasphere Ge-detector array and were correlated with the 101Sn β-delayed protons using the Recoil-Decay Tagging method. As a result, a γ-ray transition between the single-neutron vg7/2 and vd5/2 states situated at the Fermi surface was identified. The measured vg7/2-vd5/2 energy splitting was compared with predictions corresponding to various mean-field potentials and was used to calculate multi-neutron configurations in light Sn isotopes. Similar approach can be used to study core excitations in 101Sn and other exotic nuclei near 100Sn.

    L Trache, A Banu, JC Hardy, VE Iacob, M McCleskey, BT Roeder, E Simmons, A Spiridon, RE Tribble, A Saastamoinen, A Jokinen, J Äysto, T Davinson, G Lotay, PJ Woods, E Pollacco (2012)Decay spectroscopy for nuclear astrophysics: β- and β-delayed proton decay, In: Journal of Physics: Conference Series337(1)

    In several radiative proton capture reactions important in novae and XRBs, the resonant parts play the capital role. We use decay spectroscopy techniques to find these resonances and study their properties. We have developed techniques to measure beta- and beta-delayed proton decay of sd-shell, proton-rich nuclei produced and separated with the MARS recoil spectrometer of Texas A&M University. The short-lived radioactive species are produced in-flight, separated, then slowed down (from about 40 MeV/u) and implanted in the middle of very thin Si detectors. This allows us to measure protons with energies as low as 200 keV from nuclei with lifetimes of 100 ms or less. At the same time we measure gamma-rays up to 8 MeV with high resolution HPGe detectors. We have studied the decay of 23Al, 27P, 31Cl, all important for understanding explosive H-burning in novae. The technique has shown a remarkable selectivity to beta-delayed charged-particle emission and works even at radioactive beam rates of a few pps. The states populated are resonances for the radiative proton capture reactions 22Na(p,γ) 23Mg (crucial for the depletion of 22Na in novae), 26mAl(p,γ) 27Si and 30P(p,γ) 31S (bottleneck in novae and XRB burning), respectively. Lastly, results with a new detector that allowed us to measure down to about 80 keV proton energy are announced.

    Q Zhong, T Aumann, S Bishop, K Blaum, K Boretzky, F Bosch, H Bräuning, C Brandau, T Davinson, I Dillmann, O Ershova, H Geissel, G Gyürky, M Heil, F Käppeler, A Kelić, C Kozhuharov, C Langer, T Le Bleis, YA Litvinov, G Lotay, J Marganiec, N Petridis, R Plag, U Popp, R Reifarth, B Riese, C Rigollet, C Scheidenberger, H Simon, T Stöhlker, T Szücs, G Weber, H Weick, DFA Winters, N Winters, J Woods (2010)96Ru(p,γ)97Rh measurement at the GSI storage ring, In: Journal of Physics: Conference Series202

    A pioneering experiment was recently performed at the Experimental Storage Ring (ESR) at GSI. Fully stripped ions of 96Ru were injected into the storage ring and slowed down to a few MeV per nucleon. The 97Rh ions from the 96Ru(p,γ) reaction at a newly developed hydrogen jet target were detected with Double Sided Silicon Strip Detectors (DSSSD) mounted inside a pocket. The experiment and the status of the analysis at a beam energy of 11 MeV per nucleon will be presented. © 2010 IOP Publishing Ltd.

    P-A Soederstroem, PH Regan, PM Walker, H Watanabe, P Doornenbal, Z Korkulu, P Lee, HL Liu, JJ Liu, G Lorusso, S Nishimura, T Sumikama, VH Phong, J Wu, FR Xu, A Yagi, GX Zhang, T Alharbi, H Baba, F Browne, AM Bruce, R Carroll, KY Chae, Z Dombradi, A Estrade, N Fukuda, C Griffin, E Ideguchi, N Inabe, T Isobe, H Kanaoka, I Kojouharov, FG Kondev, T Kubo, S Kubono, N Kurz, I Kuti, S Lalkovski, GJ Lane, CS Lee, EJ Lee, G Lotay, C-B Moon, I Nishizuka, CR Nita, A Odahara, Z Patel, Z Podolyak, OJ Roberts, H Sakurai, H Schaffner, CM Shand, H Suzuki, H Takeda, S Terashima, Z Vajta, JJ Valiente-Dobon, ZY Xu, S Yoshida (2015)Heavy Rotation - Evolution of quadrupole collectivity centred at the neutron-rich doubly mid-shell nucleus Dy-170, In: NUCLEAR STRUCTURE AND DYNAMICS '151681
    M Assié, F De Oliveira Santos, F De Grancey, L Achouri, J Alcantara-Nunez, JC AngÉlique, C Borcea, L Caceres, I Celikovic, V Chudoba, DY Pang, T Davinson, C Ducoin, M Fallot, J Kiener, A Lefebvre-Schuhl, GL Lotay, J Mrazek, L Perrot, AM Sanchez-Benitez, F Rotaru, MG Saint-Laurent, Y Sobolev, M Stanoiu, R Stanoiu, I Stefan, K Subotic, PJ Woods, P Ujic, R Wolski (2011)Spectroscopy of the unbound nucleus 18Na, In: International Journal of Modern Physics E20(4)pp. 971-975

    The unbound nucleus 18Na, the intermediate nucleus in the two-proton radioactivity of 19Mg, is studied through the resonant elastic scattering 17Ne(p,17Ne)p. The spectroscopic information obtained in this experiment is discussed and put in perspective with previous measurements and the structure of the mirror nucleus 18N. © 2011 World Scientific Publishing Company.

    PH Regan, R Shearman, SM Judge, G Lorusso, P Main, S Bell, SM Collins, P Ivanov, SM Jerome, JD Keightley, C Larijani, G Lotay, AK Pearce (2015)Development of NANA: A Fast-Scintillator, Coincidence Gamma-ray Array for Radioactive Source Characterisation and Absolute Activity Measurements at the UK National Physical Laboratory, In: APPLICATIONS OF NOVEL SCINTILLATORS FOR RESEARCH AND INDUSTRY (ANSRI 2015)620
    D Seweryniak, MP Carpenter, S Gros, AA Hecht, N Hoteling, RV Janssens, TL Khoo, T Lauritsen, CJ Lister, G Lotay, D Peterson, AP Robinson, WB Walters, X Wang, PJ Woods, S Zhu (2007)Single-neutron states in (101)Sn., In: Phys Rev Lett99(2)pp. 022504-?

    The first data on the relative single-particle energies outside the doubly magic (100)Sn nucleus were obtained. A prompt 171.7(6) keV gamma-ray transition was correlated with protons emitted following the beta decay of (101)Sn and is interpreted as the transition between the single-neutron g(7/2) and d(5/2) orbitals in (101)Sn. This observation provides a stringent test of current nuclear structure models. The measured nug(7/2)-nud(5/2) energy splitting is compared with values calculated using mean-field nuclear potentials and is used to calculate low-energy excited states in light Sn isotopes in the framework of the shell model. The correlation technique used in this work offers possibilities for future, more extensive spectroscopy near (100)Sn.

    GJ Lotay, G Christian, C Ruiz, C Akers, DS Burke, WN Catford, AA Chen, D Connolly, B Davids, J Fallis, U Hager, DA Hutcheon, A Mahl, A Rojas, X Sun (2016)Direct Measurement of the Astrophysical 38Kðp;γÞ39Ca Reaction and Its Influence on theproduction of Nuclides toward the End Point of Nova Nucleosynthesis, In: Physical Review Letters116(13) American Physical Society

    We have performed the first direct measurement of the 38Kðp; γÞ39Ca reaction using a beam of radioactive 38K. A proposed l ¼ 0 resonance in the 38K þ p system has been identified at 679(2) keV with an associated strength of 120 þ50 −30 meV. Upper limits of 1.16 (3.5) and 8.6 (26) meV at the 68% (95%) confidence level were also established for two further expected l ¼ 0 resonances at 386 and 515 keV, respectively. The present results have reduced uncertainties in the 38Kðp; γÞ39Ca reaction rate at temperatures of 0.4 GK by more than 2 orders of magnitude and indicate that Ar and Ca may be ejected in observable quantities by oxygen-neon novae. However, based on the newly evaluated rate, the 38Kðp; γÞ39Ca path is unlikely to be responsible for the production of Ar and Ca in significantly enhanced quantities relative to solar abundances.

    D Seweryniak, K Starosta, CN Davids, S Gros, AA Hecht, N Hoteling, TL Khoo, K Lagergren, G Lotay, D Peterson, A Robinson, C Vaman, WB Walters, PJ Woods, S Zhu (2006)α decay of Te105, In: Physical Review C - Nuclear Physics73(6)

    The α decay of the neutron-deficient nuclide Te105 was observed. The Cr50(Ni58,3n) reaction was used to produce Te105 nuclei. The Te105 residues were selected with the Argonne Fragment Mass Analyzer and implanted into a double-sided Si strip detector where their subsequent α decay was detected. An α-decay Q value of Qα=4900(50) keV and a half life of T1/2=0.70(-0.17+0.25)μs were measured for Te105 and a reduced α-decay width of Wα=3.3(-1.7+2.1) was deduced. The decay properties of Te105 are compared with those of heavier Te isotopes and theoretical predictions. © 2006 The American Physical Society.

    Z Podolyak, CM Shand, E Wilson, BA Brown, H Grawe, CJ Chiara, S Zhu, B Fornal, RVF Janssens, M Bowry, M Bunce, MP Carpenter, N Cieplicka, AY Deo, GD Dracoulis, CR Hoffman, RS Kempley, FG Kondev, GJ Lane, T Lauritsen, G Lotay, MW Reed, PH Regan, CR Triguero, D Seweryniak, B Szpak, PM Walker, A Gargano, L Coraggio, N Itaco (2015)Octupole transitions in the Pb-208 region, In: 11TH INTERNATIONAL SPRING SEMINAR ON NUCLEAR PHYSICS: SHELL MODEL AND NUCLEAR STRUCTURE - ACHIEVEMENTS OF THE PAST TWO DECADES580ARTN 0pp. ?-? IOP PUBLISHING LTD
    GAVIN JAMES LOTAY, DANIEL THOMAS DOHERTY, D. Seweryniak, M.P. Carpenter, R. V. F. Janssens, J Jose, A. M. Rogers, P. J. Woods, S. Zhu (2020)Spectroscopy of 30 P and the abundance of 29 Si in presolar grains, In: PHYSICAL REVIEW C102(3)35804 American Physical Society

    The astrophysical 29 Si(p, γ) reaction is expected to play a key role in determining the final 29 Si yields ejected in nova explosions. Such yields are used to accurately identify the stellar origins of meteoritic stardust and recently, distinctive silicon isotopic ratios have been extracted from a number of presolar grains. Here, the light-ion 28 Si(3 He, p) fusion-evaporation reaction was used to populate low-spin proton-unbound excited states in the nucleus 30 P that govern the rate of the astrophysical 29 Si(p, γ) reaction. In particular, γ decays were observed from resonances up to E r = 500 keV, and key resonances at 217 and 315 keV have now been identified as 2 + and 2 − levels, respectively. The present paper provides the first estimate of the 217-keV resonance strength and indicates that the strength of the 315-keV resonance, which dominates the rate of the 29 Si(p, γ) reaction over the entire peak temperature range of oxygen-neon novae, is higher than previously expected. As such, the abundance of 29 Si ejected during nova explosions is likely to be less than that predicted by the most recent theoretical models.

    K Auranen, D Seweryniak, M Albers, A.D Ayangeakaa, S Bottoni, M.P Carpenter, C.J Chiara, P Copp, H.M David, D.T Doherty, J Harker, C.R Hoffman, R.V.F Janssens, T.L Khoo, S.A Kuvin, T Lauritsen, G Lotay, A.M Rogers, C Scholey, R Talwar, J Sethi, W.B Walters, P.J Woods, S Zhu (2019)Proton decay of 108I and its significance for the termination of the astrophysical rp-process, In: Physics Letters. B792(C)pp. 187-192 Elsevier B.V

    Employing the Argonne Fragment Mass Analyzer and the implantation-decay-decay correlation technique, a weak 0.50(21)% proton decay branch was identified in 108I for the first time. The 108I proton-decay width is consistent with a hindered l=2 emission, suggesting a d52 origin. Using the extracted 108I proton-decay Q value of 597(13) keV, and the Qα values of the 108I and 107Te isotopes, a proton-decay Q value of 510(20) keV for 104Sb was deduced. Similarly to the 112,113Cs proton-emitter pair, the Qp(I108) value is lower than that for the less-exotic neighbor 109I, possibly due to enhanced proton-neutron interactions in N≈Z nuclei. In contrast, the present Qp(Sb104) is higher than that of 105Sb, suggesting a weaker interaction energy. For the present Qp(Sb104) value, network calculations with the one-zone X-ray burst model Mazzocchi et al. (2007) [18] predict no significant branching into the Sn-Sb-Te cycle at 103Sn.

    J Henderson, P Ruotsalainen, DG Jenkins, C Scholey, K Auranen, PJ Davies, T Grahn, PT Greenlees, TW Henry, A Herzáň, U Jakobsson, P Joshi, R Julin, S Juutinen, J Konki, M Leino, G Lotay, AJ Nichols, A Obertelli, J Pakarinen, J Partanen, P Peura, P Rahkila, M Sandzelius, J Sarén, J Sorri, S Stolze, J Uusitalo, R Wadsworth (2013)Enhancing the sensitivity of recoil-beta tagging, In: Journal of Instrumentation8(4)

    Tagging with β-particles at the focal plane of a recoil separator has been shown to be an effective technique for the study of exotic proton-rich nuclei. This article describes three new pieces of apparatus used to greatly improve the sensitivity of the recoil-beta tagging technique. These include a highly-pixelated double-sided silicon strip detector, a plastic phoswich detector for discriminating high-energy β-particles, and a charged-particle veto box. The performance of these new detectors is described and characterised, and the resulting improvements are discussed.© 2013 IOP Publishing Ltd and Sissa Medialab srl.

    M Debenham, M Bentley, J Davies, H Haylett, G Jenkins, P Joshi, L Sinclair, R Wadsworth, P Ruotsalainen, J Henderson, K Kaneko, K Auranen, H Badran, T Grahn, P Greenlees, A Herzaáň, U Jakobsson, J Konki, R Julin, M Leino, S Juutinen, J Sorri, J Pakarinen, P Papadakis, P Peura, J Partanen, P Rahkila, M Sandzelius, J Sarén, C Scholey, S Stolze, J Uusitalo, H.M David, G De Angelis, W Korten, G Lotay, M Mallaburn, Evren Sahin (2016)Spectroscopy of 70Kr and isospin symmetry in the T = 1 f pg shell nuclei, In: Physical Review. C, Nuclear Physics9454311 American Physical Society

    The recoil-β tagging technique has been used in conjunction with the 40 Ca(32 S ,2n) reaction at a beam energy of 88 MeV to identify transitions associated with the decay of the 2 + and, tentatively, 4 + states in the nucleus 70 Kr. These data are used, along with previously published data, to examine the triplet energy differences (TED) for the mass 70 isobars. The experimental TED values are compared with shell model calculations, performed with the JUN45 interaction in the fpg model space, that include a J = 0 isospin nonconserving (INC) interaction with an isotensor strength of 100 keV. The agreement is found to be very good up to spin 4 and supports the expectation for analog states that all three nuclei have the same oblate shape at low-spin. The A = 70 results are compared with the experimental and shell model predicted TED and mirror energy differences (MED) for the mass 66 and 74 systems. The comparisons clearly demonstrate the importance of the isotensor INC interaction in replicating the TED data in this region. Issues related to the observed MED values and their interpretation within the shell model are discussed.

    RHIANN CANAVAN, M. Rudigier, PATRICK HENRY REGAN, D. Thisse, M. Lebois, J N Wilson, N. Jovancevic, P.-A. Söderström, SEAN MICHAEL COLLINS, Jaime Benito García, S. Bottoni, MATTHEW HENRY BRUNET, N. Cieplicka-Orynczak, S. Courtin, DANIEL THOMAS DOHERTY, Luis Mario Fraile Prieto, K. Hadynska-Klek, G. Hafner, M. Heine, V. Karayonchev, Ł.W. Iskra, ADAM RUSSELL KENNINGTON, P. Koseoglou, GAVIN JAMES LOTAY, G Lorusso, M Nakhostin, C.R. Nita, S. Oberstedt, ZSOLT PODOLYAK, L Qi, J.-M. Régis, V. Sánchez-Tembleque, R Shearman, María Victoria Vedia Fernández, W. Witt (2020)Half-life measurements in Dy-164,Dy-166 using γ−γ fast-timing spectroscopy with the ν-Ball spectrometer, In: Physical Review. C101(2) American Physical Society

    We report on the measurement of lifetimes of excited states in the near-mid-shell nuclei Dy-164,Dy-166 using the gamma-ray coincidence fast-timing method. The nuclei of interest were populated using reactions between an O-18 beam and a gold-backed isotopically enriched Dy-164 target of thickness 6.3 mg/cm(2) at primary beam energies of 71, 76, and 80 MeV from the IPN-Orsay laboratory, France. Excited states were populated in Dy-164, Dy-166, and W-178,W-179 following Coulomb excitation, inelastic nuclear scattering, two-neutron transfer, and fusion-evaporation reaction channels respectively. Gamma rays from excited states were measured using the nu-Ball high-purity germanium (HPGe)-LaBr3 hybrid gamma-ray spectrometer with the excited state lifetimes extracted using the fast-timing coincidence method using HPGe-gated LaBr3-LaBr3 triple coincident events. The lifetime of the first I-pi = 2(+) excited state in Dy-166 was used to determine the transition quadrupole deformation of this neutron-rich nucleus for the first time. The experimental methodology was validated by showing consistency with previously determined excited state lifetimes in Dy-164. The half-lives of the yrast 2(+) states in Dy-164 and Dy-166 were 2.35(6) and 2.3(2) ns, respectively, corresponding to transition quadrupole moment values of Q(0) = 7.58(9) and 7.5(4) eb, respectively. The lifetime of the yrast 2(+) state in Dy-166 is consistent with a quenching of nuclear quadrupole deformation at beta approximate to 0.35 as the N = 104 mid-shell is approached.

    K Auranen, D Seweryniak, M Albers, A. D Ayangeakaa, S Bottoni, M. P Carpenter, C. J Chiara, P Copp, H. M David, D. T Doherty, J Harker, C. R Hoffman, R. V. F Janssens, T. L Khoo, S. A Kuvin, T Lauritsen, G Lotay, A. M Rogers, J Sethi, C Scholey, R Talwar, W. B Walters, P. J Woods, S Zhu (2018)Superallowed alpha Decay to Doubly Magic Sn-100, In: Physical Review Letters121(18) American Physical Society

    We report the first observation of the 108Xe → 104Te → 100Sn α-decay chain. The α emitters, 108Xe [Eα ¼ 4.4ð2Þ MeV, T1=2 ¼ 58þ106 −23 μs] and 104Te [Eα ¼ 4.9ð2Þ MeV, T1=2 < 18 ns], decaying into doubly magic 100Sn were produced using a fusion-evaporation reaction 54Feð58Ni; 4nÞ108Xe, and identified with a recoil mass separator and an implantation-decay correlation technique. This is the first time α radioactivity has been observed to a heavy self-conjugate nucleus. A previous benchmark for study of this fundamental decay mode has been the decay of 212Po into doubly magic 208Pb. Enhanced proton-neutron interactions in the N ¼ Z parent nuclei may result in superallowed α decays with reduced α-decay widths significantly greater than that for 212Po. From the decay chain, we deduce that the α-reduced width for 108Xe or 104Te is more than a factor of 5 larger than that for 212Po.

    G Lotay, JP Wallace, PJ Woods, D Seweryniak, MP Carpenter, CJ Chiara, DT Doherty, RVF Janssens, T Lauritsen, AM Rogers, S Zhu (2012)Erratum: Level structure of 30S: Implications for the astrophysical 29P(p,γ)30S reaction rate in ONe novae and x-ray bursts(Physical Review C (2012) 86 (042801)), In: Physical Review C - Nuclear Physics86(4)
    HM David, PJ Woods, G Lotay, D Seweryniak, M Albers, M Alcorta, MP Carpenter, CJ Chiara, T Davinson, DT Doherty, CR Hoffman, RVF Janssens, T Lauritsen, AM Rogers, S Zhu (2013)Low-lying T=0 states in the odd-odd N=Z nucleus 62Ga, In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics726(4-5)pp. 665-669

    New, low-lying levels in the odd-odd, N=Z nucleus 62Ga have been identified using a sensitive technique, where in-beam γ rays from short-lived nuclei are tagged with β decays following recoil mass identification. A comparison of the results with shell-model and IBM-4 calculations demonstrates good agreement between theory and experiment, with the majority of predicted low-lying, low-spin T=0 states now identified. There is a dramatic change in the level density at low excitation energies for the N=Z nucleus 62Ga when compared with neighbouring odd-odd Ga isotopes where, in contrast, the low-lying level structure is dominated by configurations with T=1 pairing interactions between excess neutrons. This illustrates the distinctively different aspects of nuclear structure exhibited by nuclei with N=Z. © 2013 Elsevier B.V.

    G Lotay, D. T Doherty, D Seweryniak, S Almaraz-Calderon, M. P Carpenter, C. J Chiara, H. M David, C. R Hoffman, R. V. F Janssens, A Kankainen, T Lauritsen, R Wilkinson, P. J Woods, S Zhu (2019)Identification of $\gamma$-decaying resonant states in 26Mg and their importance for the astrophysical s process, In: The European Physical Journal. A, Hadrons and nuclei55109 Springer

    The 22Ne(α, n) reaction is expected to provide the dominant neutron source for the weak s process in massive stars and intermediate-mass (IM) Asymptotic Giant Branch (AGB) stars. However, the production of neutrons in such environments is hindered by the competing 22Ne(α,γ)26Mg reaction. Here, the 11B(16O,p) fusion-evaporation reaction was used to identify γ-decay transitions from 22Ne + α resonant states in 26Mg. Spin-parity restrictions have been placed on a number of α-unbound excited states in 26 Mg and their role in the 22Ne(α,γ)26Mg reaction has been investigated. In particular, a suspected natural-parity resonance at Ec.m. = 557(3) keV, that lies above the neutron threshold in 26Mg, and is known to exhibit a strong α-cluster character, was observed to γ decay. Furthermore, a known resonance at Ec.m.= 466(4) keV has been definitively assigned 2+ spin and parity. Consequently, uncertainties in the 22Ne(α,γ) stellar reaction rate have been reduced by a factor of ~20 for temperatures ~0.2 GK.

    R.J Carroll, Philip M Walker, Gregory Lane, Matthew Reed, Aqeel Akber, H.M Albers, J.J Carroll, D M Cullen, A.C Dai, C Fahlander, Matthew Gerathy, Sankha Hota, G Lotay, Tibor Kibedi, V Margerin, Alan John Mitchell, Nyaladzi Palalani, Thomas Palazzo, Z Patel, Andrew Stuchbery (2020)γ-ray spectroscopy of a four-quasiparticle isomer band in 174Re, In: Physical Review C101054314 American Physical Society

    Excited states in 174Re have been populated in fusion-evaporation reactions at the Australian National University, and γ-ray spectroscopy has been used to determine the level structure and to deduce the underlying nucleon configurations. The half-life of the bandhead of the Kπ=8−band has been measured to be 2.7(4) ns. A band built on an isomeric state of spin-parity (14−) and a half-life of 53(5) ns has been observed here for the first time, and has been determined to have a four-quasiparticle structure. Contrasting reduced-hindrance values for its decay are discussed in terms of deformation and configuration changes, as indicated by configuration-constrained potential energy surface calculations. The technical staff at the ANU 14UD accelerator facility are thanked for their excellent support. Funding is acknowledged from the UK Science and Technology Facilities Council under Grant No. ST/P005314/1Support for the ANU Heavy Ion Accelerator Facility operations through the Australian National Collaborative Research Infrastructure Strategy (NCRIS) program is acknowledged.

    A.  R. L Kennington, G Lotay, D. T Doherty, D Seweryniak, C Andreoiu, K Auranen, M. P Carpenter, W. N Catford, C. M Deibel, K Hadyńska-Klęk, S Hallam, D. E. M Hoff, T Huang, R. V. F Janssens, S Jazrawi, J José, F. G Kondev, T Lauritsen, J Li, A. M Rogers, J Saiz, G Savard, S Stolze, G. L Wilson, S Zhu (2020)Search for Nova Presolar Grains: $γ$-Ray Spectroscopy of 34Ar and its Relevance for the Astrophysical 33Cl($p,γ$) Reaction, In: Physical Review Letters124(25) American Physical Society (APS)

    The discovery of presolar grains in primitive meteorites has launched a new era of research in the study of stellar nucleosynthesis. However, the accurate classification of presolar grains as being of specific stellar origins is particularly challenging. Recently, it has been suggested that sulfur isotopic abundances may hold the key to definitively identifying presolar grains with being of nova origins and, in this regard, the astrophysical Cl33 ( p,γ ) Ar34 reaction is expected to play a decisive role. As such, we have performed a detailed γ -ray spectroscopy study of Ar34 . Excitation energies have been measured with high precision and spin-parity assignments for resonant states, located above the proton threshold in Ar34 , have been made for the first time. Uncertainties in the Cl33 ( p,γ ) reaction have been dramatically reduced and the results indicate that a newly identified ℓ=0 resonance at Er=396.9 ( 13 ) keV dominates the entire rate for T=0.25–0.40 GK . Furthermore, nova hydrodynamic simulations based on the present work indicate an ejected S 32/ S 33 abundance ratio distinctive from type-II supernovae and potentially compatible with recent measurements of a presolar grain.

    E McCleskey, A Banu, M McCleskey, T Davinson, D. T Doherty, G Lotay, B. T Roeder, A Saastamoinen, A Spiridon, L Trache, J. P Wallace, P. J Woods, R. E Tribble (2016)Simultaneous measurement of β -delayed proton and γ decay of P 27, In: Physical Review. C94(6) American Physical Society

    This is the first study of 27P to measure both the β-delayed proton and β-delayed γ decays. While no new proton groups in the astrophysically interesting energy region of 300–400 keV were observed, a new upper limit on the proton branching of 0.16% was estimated. Several new γ -ray lines were observed, mainly coming from the isobaric analog state in 27Si, which has been assigned a more accurate energy value of 6638(1) keV.

    J. J Liu, J Lee, H Watanabe, S Nishimura, G. X Zhang, J Wu, P. M Walker, P. H Regan, P. -A Söderström, H Kanaoka, Z Korkulu, P. S Lee, A Yagi, A. C Dai, F. R Xu, D. S Ahn, T Alharbi, H Baba, F Browne, A. M Bruce, R. J Carroll, K. Y Chae, Zs Dombradi, P Doornenbal, A Estrade, N Fukuda, C Griffin, E Ideguchi, N Inabe, T Isobe, S Kanaya, I Kojouharov, F. G Kondev, T Kubo, S Kubono, N Kurz, I Kuti, S Lalkovski, G. J Lane, C. S Lee, E. J Lee, G Lorusso, G Lotay, C. -B Moon, I Nishizuka, C. R Nita, A Odahara, Z Patel, V. H Phong, Zs Podolyák, O. J Roberts, H Sakurai, H Schaffner, C. M Shand, Y Shimizu, T Sumikama, H Suzuki, H Takeda, S Terashima, Zs Vajta, J. J Valiente-Dobón, Z. Y Xu (2020)Isomeric and beta-decay spectroscopy of 173,174Ho, In: Physical Review. C, Nuclear Physics102(2) American Physical Society (APS)

    β-decay spectroscopy of 173,174Ho (Z = 67, N = 106,107) was conducted at Radioactive Isotope Beam Factory at RIKEN by using in-flight fission of a 345-MeV/u 238U primary beam. A previously unreported isomeric state at 405 keV with half-life of 3.7(12) μs and a spin and parity of (3/2+) is identified in 173Ho. Moreover, a new state with a spin and parity of 9- was discovered in 174Er. The experimental log ft values of 5.84(20) and 5.25(18) suggest an allowed-hindered β decay from the ground state of 174Ho to the Kπ = 8- isomeric state in 174Er. Configuration-constrained potential energy surface (PES) calculations were performed and the predictions are in reasonable agreement with the experimental results.

    RHIANN CANAVAN, M Rudigier, PATRICK HENRY REGAN, M Lebois, JULIET WILSON, N Jovancevic, P.-A Söderström, D Thisse, J Benito, S Bottoni, MATTHEW HENRY BRUNET, N Cieplicka-Oryńczak, SEAN MICHAEL COLLINS, S Courtin, DANIEL THOMAS DOHERTY, L.M Fraile, K Hadyńska-Klęk, M Heine, Ł.W Iskra, V Karayonchev, ADAM RUSSELL KENNINGTON, P Koseoglou, GAVIN JAMES LOTAY, G Lorusso, M Nakhostin, C.R Niţă, S Oberstedt, Zs Podolyák, L Qi, J.-M Régis, R Shearman, V Vedia, W Witt (2020)Reaction Channel selection techniques and γ - γ fast-timing spectroscopy using the ν-Ball Spectrometer, In: Journal of physics. Conference series1643(1) IOP Publishing

    The reaction of a pulsed 18O beam on a self-supporting and gold-backed isotopically-enriched 164Dy target of thickness 6.3 mg/cm2 at separate primary beam energies of 71, 76 and 80 MeV was studied at the accelerator at the ALTO facility of the IPN Orsay. The γ rays produced were detected using the newly-constructed ν-Ball spectrometer which comprised of HPGe and LaBr3(Ce) detectors. This conference paper describes the methodology and effectiveness of multiplicity/sum-energy gating, for channel selection between fusion evaporation events and lower multiplicity/energy events from inelastic nuclear scattering and Coulomb excitation of the target, and from two-neutron transfer reactions to 166Dy.

    SHAHEEN JAZRAWI, DANIEL THOMAS DOHERTY, J.M Allmond, PATRICK HENRY REGAN, R.V.F Janssens, W Korten, S Zhu, M Zielińska, D Radford, S Ansari, K Auranen, B Bucher, M.P Carpenter, WILTON NEIL CATFORD, K Hadyńska-Klek, JACK HENDERSON, M Hendricks, M Komorowska, F.G Kondev, T Lauritsen, JUERONG LI, GAVIN JAMES LOTAY, P.J Napiorkowski, E Padilla-Rodal, R.C Pardo, B.C Rasco, W Reviol, D.G Sarantites, D Seweryniak, D Santiago-Gonzalez, G Savard, P Singh, S.M Stolze, R Vondrasek, G Wilson, CHUAN-YU WU, J Wu (2020)A High-Resolution Study of the 110Tc → 110Ru → 110Rh → 110Pd Decay Chain with the GRETINA Array, In: Journal of Physics. Conference Series1643(1) IOP Publishing

    Spectroscopic data, such as precise γ-ray branching and E2/M1 multipole-mixing ratios, provide vital constraints when performing multi-dimensional Coulomb-excitation analyses. Consequently, as part of our new Coulomb-excitation campaign aimed at investigating the role of exotic non-axial (triaxial) deformations in the unstable refractory Ru-Mo isotopes, additional beta-decay data was obtained. These measurements make use of ANL's CARIBU facility, which provides intense beams of radioactive refractory isotopes along with the excellent efficiency and angular resolution of the GRETINA γ-ray tracking array. In this article, we report on the analysis of the A = 110 decay chain, focussing on the identification of previously unreported states in 110Ru following the decay of 110Tc.

    G Lotay, JP Wallace, PJ Woods, D Seweryniak, MP Carpenter, CJ Chiara, DT Doherty, RVF Janssens, T Lauritsen, AM Rogers, S Zhu (2012)Level structure of 30S: Implications for the astrophysical 29P(p,γ)30S reaction rate in ONe novae and x-ray bursts, In: Physical Review C - Nuclear Physics86(4)

    A γ-ray spectroscopy study of 30S is presented. Excitation energies have been determined with improved precision over previous studies and firm spin-parity assignments have been made for key 29P+p resonant states. An evaluation of the 29P(p,γ)30S reaction for T=0.08-2.5 GK shows that the 3 + and 2 + resonant states located at E r=289(3) and 410(3) keV, respectively, dominate the 29P(p,γ)30S reaction rate in ONe novae, while the 410-keV resonance is expected to govern the rate in x-ray burster environments. These new, precise resonance energy measurements and firm spin-parity assignments have significantly reduced uncertainties in the 29P(p,γ)30S reaction in ONe novae and x-ray bursts. In particular, the reaction rate is now specified precisely enough for calculations of isotopic abundances in ONe novae ejecta. © 2012 American Physical Society.

    PJC Salter, M Aliotta, T Davinson, H Al Falou, A Chen, B Davids, BR Fulton, N Galinski, D Howell, G Lotay, P MacHule, ASJ Murphy, C Ruiz, S Sjue, M Taggart, P Walden, PJ Woods (2012)Erratum: Measurement of the Ne18(α,p 0)Na21 reaction cross section in the burning energy region for X-ray bursts (Physical Review Letters (2012) 108 (242701)), In: Physical Review Letters109(6)
    Yang Sun, G.X. Zhang, H. Watanabe, F.G. Kondev, G.J. Lane, P.H. Regan, P.-A. Söderström, P.M. Walker, H. Kanaoka, Z. Korkulu, P.S Lee, J.J Liu, S. Nishimura, J. Wu, A. Yagi, D.S. Ahn, T. Alharbi, H. Baba, F. Browne, A.M. Bruce, R.J. Carroll, K.Y. Chae, Zs. Dombradi, P. Doornenbal, A. Estrade, N. Fukuda, C. Griffin, E. Ideguchi, N. Inabe, T. Isobe, S. Kanaya, I. Kojouharov, T. Kubo, S. Kubono, N. Kurz, I. Kuti, S. Lalkovski, C.S. Lee, E.J. Lee, G. Lorusso, G. Lotay, C.-B Moon, I. Nishizuka, C.R. Nita, A. Odahara, Z. Patel, V.H. Phong, Zs. Podolyak, O.J. Roberts, H. Sakurai, H. Schaffner, C.M. Shand, Y. Shimizu, T. Sumikama, H. Suzuki, H. Takeda, S. Terashima, Zs. Vajta, J.J. Valiente-Dóbon, Z.Y. Xu (2018)β-γ and isomeric decay spectroscopy of 168Dy, In: EPJ Web of Conferences178pp. 02023-1 EDP Sciences

    This contribution will report on the experimental work on the level structure of 168Dy. The experimental data have been taken as part of the EURICA decay spectroscopy campaign at RIBF, RIKEN in November 2014. In the experiment, a 238U primary beam is accelerated up to 345 MeV/u with an average intensity of 12 pnA. The nuclei of interest are produced by in-flight fission of 238U impinging on Be target with a thickness of 5 mm. The excited states of 168Dy have been populated through the decay from a newly identified isomeric state and via the β decay from 168Tb. In this contribution, scientific motivations, experimental procedure and some preliminary results for this study are presented.

    DT Doherty, PJ Woods, G Lotay, D Seweryniak, MP Carpenter, CJ Chiara, HM David, RVF Janssens, L Trache, S Zhu (2014)Level structure of S 31: From low excitation energies to the region of interest for hydrogen burning in novae through the P 30 (p, γ) S 31 reaction, In: Physical Review C - Nuclear Physics89(4)

    Comprehensive measurements of the excitation energy and spin-parity assignments for states in S31 are presented, from the first excited state, up to energies relevant for the P30(p,γ)S31 reaction in ONe novae. This reaction rate strongly influences heavy element abundances in novae ejecta. States in S31 are paired with their P31 analogues using γ rays detected with the Gammasphere detector array following the Si28(He4, n) fusion-evaporation reaction. The evolution of mirror energy differences is explored and the results are compared with new shell-model calculations. The excellent agreement observed in this work between experimental data and shell-model calculations provides confidence in using computed estimates in situations where experimental data are unavailable. © 2014 American Physical Society.

    E Wilson, Z Podolyak, H Grawe, BA Brown, CJ Chiara, S Zhu, B Fornal, RVF Janssens, CM Shand, M Bowry, M Bunce, MP Carpenter, N Cieplicka-Orynczak, AY Deo, GD Dracoulis, CR Hoffman, RS Kempley, FG Kondev, GJ Lane, T Lauritsen, G Lotay, MW Reed, PH Regan, CR Triguero, D Seweryniak, B Szpak, PM Walker (2015)Core excitations across the neutron shell gap in Tl-207, In: PHYSICS LETTERS B747pp. 88-92 ELSEVIER SCIENCE BV

    The single closed-neutron-shell, one proton-hole nucleus 207Tl was populated in deep-inelastic collisions of a 208Pb beam with a 208Pb target. The yrast and near-yrast level scheme has been established up to high excitation energy, comprising an octupole phonon state and a large number of core excited states. Based on shell-model calculations, all observed single core excitations were established to arise from the breaking of the N=126 neutron core. While the shell-model calculations correctly predict the ordering of these states, their energies are compressed at high spins. It is concluded that this compression is an intrinsic feature of shell-model calculations using two-body matrix elements developed for the description of two-body states, and that multiple core excitations need to be considered in order to accurately calculate the energy spacings of the predominantly three-quasiparticle states.

    Laila Gurgi, Patrick Regan, P-A Söderström, H Watanabe, Philip Walker, Zsolt Podolyak, S Nishimura, Thomas Berry, P Doornenbal, G Lorusso, T Isobe, H Baba, ZY Xu, H Sakurai, T Sumikama, Wilton Catford, AM Bruce, F Browne, GJ Lane, FG Kondev, A Odahara, J Wu, HL Liu, FR Xu, Z Korkulu, P Lee, JJ Liu, VH Phong, A Yagi, GX Zhang, T Alharbi, RJ Carroll, KY Chae, Z Dombradi, A Estrade, N Fukuda, C Griffin, E Ideguchi, N Inabe, H Kanaoka, I Kojouharov, T Kubo, S Kubono, N Kurz, I Kuti, S Lalkovski, EJ Lee, CS Lee, Gavin Lotay, CB Moon, I Nishizuka, CR Nita, Z Patel, OJ Roberts, H Schaffner, Callum Shand, H Suzuki, H Takeda, S Terashima, Z Vajta, S Kanaya, J-J Valiente-Dobón (2017)Isomer Spectroscopy of Neutron-rich 165,167Tb, In: Acta Physica Polonica B48(3)pp. 601-608

    We present information on the excited states in the prolate-deformed, neutron-rich nuclei 165;167Tb100;102. The nuclei of interest were synthesised following in-flight fission of a 345 MeV per nucleon 238U primary beam on a 2 mm 9Be target at the Radioactive Ion-Beam Factory (RIBF), RIKEN, Japan. The exotic nuclei were separated and identified event-by-event using the BigRIPS separator, with discrete energy gamma-ray decays from isomeric states with half-lives in the s regime measured using the EURICA gamma-ray spectrometer. Metastable-state decays are identified in 165Tb and 167Tb and interpreted as arising from hindered E1 decay from the 7 2 [523] single quasi-proton Nilsson configuration to rotational states built on the 3 2 [411] single quasi-proton ground state. These data correspond to the first spectroscopic information in the heaviest, odd-A terbium isotopes reported to date and provide information on proton Nilsson configurations which reside close to the Fermi surface as the 170Dy doubly-midshell nucleus is approached.

    P Ruotsalainen, DG Jenkins, MA Bentley, K Auranen, PJ Davies, T Grahn, PT Greenlees, J Henderson, A Herzáň, U Jakobsson, P Joshi, R Julin, S Juutinen, J Konki, M Leino, G Lotay, AJ Nichols, A Obertelli, J Pakarinen, J Partanen, P Peura, P Rahkila, M Sandzelius, J Sarén, C Scholey, J Sorri, S Stolze, J Uusitalo, R Wadsworth (2013)Spectroscopy of proton-rich 66^Se up to J^π = 6^+: isospin-breaking effect in the A = 66 isobaric triplet

    Candidates for three excited states in the 66^Se have been identified using the recoil-{_beta} tagging method together with a veto detector for charged-particle evaporation channels. These results allow a comparison of mirror and triplet energy differences between analogue states across the A = 66 triplet as a function of angular momentum. The extracted triplet energy differences follow the negative trend observed in the f_7/2 shell. Shell-model calculations indicate a continued need for an additional isospin non-conserving interaction in addition to the Coulomb isotensor part as a function of mass.

    B Mei, T Aumann, S Bishop, K Blaum, K Boretzky, F Bosch, C Brandau, H Bräuning, T Davinson, I Dillmann, C Dimopoulou, O Ershova, Z Fülöp, H Geissel, J Glorius, G Gyürky, M Heil, F Käppeler, A Kelic-Heil, C Kozhuharov, C Langer, TL Bleis, Y Litvinov, G Lotay, J Marganiec, G Münzenberg, F Nolden, N Petridis, R Plag, U Popp, G Rastrepina, R Reifarth, B Riese, C Rigollet, C Scheidenberger, H Simon, K Sonnabend, M Steck, T Stöhlke, T Szücs, K Sümmerer, G Weber, H Weick, D Winters, N Winters, P Woods, Q Zhong (2015)First Measurement of the $^{96}$Ru(p,$γ$)$^{97}$Rh Cross Section for the p-Process with a Storage Ring, In: Phys. Rev. C92pp. 035803-?

    This work presents a direct measurement of the $^{96}$Ru($p, ____gamma$)$^{97}$Rh cross section via a novel technique using a storage ring, which opens opportunities for reaction measurements on unstable nuclei. A proof-of-principle experiment was performed at the storage ring ESR at GSI in Darmstadt, where circulating $^{96}$Ru ions interacted repeatedly with a hydrogen target. The $^{96}$Ru($p, ____gamma$)$^{97}$Rh cross section between 9 and 11 MeV has been determined using two independent normalization methods. As key ingredients in Hauser-Feshbach calculations, the $____gamma$-ray strength function as well as the level density model can be pinned down with the measured ($p, ____gamma$) cross section. Furthermore, the proton optical potential can be optimized after the uncertainties from the $____gamma$-ray strength function and the level density have been removed. As a result, a constrained $^{96}$Ru($p, ____gamma$)$^{97}$Rh reaction rate over a wide temperature range is recommended for $p$-process network calculations.

    S Courtin, G Fruet, DG Jenkins, M Heine, D Montanari, LG Morris, Gavin Lotay, Patrick Regan, OS Kirsebom, S Della Negra, F Hammache, N De Sereville, B Bastin, F de Oliveira, G Randisi, C Stodel, C Beck, F Haas (2017)Fusion Cross Sections of Astrophysics Interest Within the STELLA Project., In: Proceedings of the 14th International Symposium on Nuclei in the Cosmos (NIC2016) 2017021001 Physical Society of Japan

    Low energy fusion between light heavy-ions is a key feature of the evolution of massive stars. In systems of astrophysical interest, the process may be strongly affected by molecular configurations of the compound nucleus, leading to resonant S factors. In particular, the 12C+12C fusion reaction has been the object of numerous experimental investigations. The STELLA project has been developed to extend these investigations to lower energies towards the Gamow window.

    V Margerin, ASJ Murphy, T Davinson, R Dressler, J Fallis, A Kankainen, AM Laird, G Lotay, DJ Mountford, CD Murphy, C Seiffert, D Schumann, T Stowasser, T Stora, CHT Wang, PJ Woods (2014)Study of the Ti44(α,p)V47 reaction and implications for core collapse supernovae, In: Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics731pp. 358-391

    The underlying physics triggering core collapse supernovae is not fully understood but observations of material ejected during such events helps to solve this puzzle. In particular, several satellite based γ-ray observations of the isotope 44Ti have been reported recently. Conveniently, the amount of this isotope in stellar ejecta is thought to depend critically on the explosion mechanism. The most influential reaction to the amount of 44Ti in supernovae is Ti44(α,p)V47. Here we report on a direct study of this reaction conducted at the REX-ISOLDE facility, CERN. The experiment was performed with a 44Ti beam at Elab = 2.16MeV/u, corresponding to an energy distribution, for reacting α-particles, centred on Ecm = 4.15 with a 1σ width of 0.23 MeV. This is, for the first time, well within the Gamow window for core collapse supernovae. The material from which the 44Ti beam was extracted originates from highly irradiated components of the SINQ spallation neutron source of the Paul Scherrer Institute. No yield above background was observed, enabling an upper limit for the rate of this reaction to be determined. This result is below expectation, suggesting that the Ti44(α,p)V47 reaction proceeds more slowly than previously thought. Implications for astrophysical events, and remnant age, are discussed. © 2014 The Authors.

    M. Rudigier, R.L. Canavan, P.H. Regan, P.-A. Söderström, M. Lebois, J.N. Wilson, N. Jovancevic, S. Bottoni, M. Brunet, N. Cieplicka-Orynczak, S. Courtin, D.T. Doherty, K. Hadynska-Klek, M. Heine, W. Iskra, V. Karayonchev, A. Kennington, P. Koseoglou, G. Lotay, G. Lorusso, M. Nakhostin, C.R. Nita, S. S. Oberstedt, Zs. Podolyak, L. Qi, J.-M. Régis, R. Shearman, P.M. Walker, W. Witt (2019)Isomer spectroscopy and sub-nanosecond half-live determination in 178w using the NuBall array, In: Acta Physica Polonica B50(3)pp. 661-667 Jagiellonian University

    The reaction of a pulsed 18O beam on a 164Dy target was studied in the first experiment with the NuBall array at the IPN Orsay, France. Excited state half-lives were measured using the fast timing method with 20 LaBr3(Ce) detectors. The timing characteristics of the fully digital acquisition system is briefly discussed. A value for the previously unknown half-life of the first excited 4+ state in 178W is presented.

    E. R. Gamba, A. M. Bruce, S. Lalkovski, M. Rudigier, S. Bottoni, M. P. Carpenter, S. Zhu, J. T. Anderson, A. D. Ayangeakaa, T. A. Berry, I. Burrows, M. Carmona Gallardo, R. J. Carroll, P. Copp, D. M. Cullen, T. Daniel, G. Fernández Martínez, J. P. Greene, L. A. Gurgi, D. J. Hartley, R. Ilieva, S. Ilieva, F. G. Kondev, T. Kröll, G. J. Lane, T. Lauritsen, I. Lazarus, G. Lotay, C. R. Niţă, Zs. Podolyak, V. Pucknell, M. Reed, P. H. Regan, J. Rohrer, J. Sethi, D. Seweryniak, C. M. Shand, J. Simpson, M. Smoleń, E. A. Stefanova, V. Vedia, O. Yordanov (2019)Fast-timing measurements in the ground-state band of ¹¹⁴Pd, In: Physical Review C100(4)044309 American Physical Society

    Using a hybrid Gammasphere array coupled to 25 LaBr3(Ce) detectors, the lifetimes of the first three levels of the yrast band in ¹¹⁴Pd populated via ²⁵²Cf decay, have been measured. The measured lifetimes are τ₂+=103(10)ps, τ₄+=22(13)ps, and τ₆+≤10ps for the 2⁺₁, 4⁺₁, and 6⁺₁ levels, respectively. Palladium-114 was predicted to be the most deformed isotope of its isotopic chain, and spectroscopic studies have suggested it might also be a candidate nucleus for low-spin stable triaxiality. From the lifetimes measured in this work, reduced transition probabilities B(E2;J→J−2) are calculated and compared with interacting boson model, projected shell model, and collective model calculations from the literature. The experimental ratio RB(E₂)=B(E2;4⁺₁→2⁺₁)/B(E2;2⁺₁→0⁺₁)=0.80(42) is measured for the first time in ¹¹⁴Pd and compared with the known values RB(E₂) in the palladium isotopic chain: the systematics suggest that, for N=68, a transition from γ-unstable to a more rigid γ-deformed nuclear shape occurs.

    DG Jenkins, A Meadowcroft, NS Pattabiraman, D Seweryniak, CJ Lister, MP Carpenter, RVF Janssens, KE Rehm, T Lauritsen, S Zhu, PJ Woods, T Davinson, GJ Lotay, J José (2009)Indirect nuclear physics techniques for studying nova nucleosynthesis, In: AIP Conference Proceedings1098pp. 82-87

    Classical novae are a site of explosive nucleosynthesis where hydrogen rich material from a companion giant star accretes onto the surface of a white warf. Critical to our understanding of nova explosions are proton-capture reaction rates involved in the nucleosynthesis. While, ideally, all of the relevant (p,γ) reactions would be measured directly, in practice, such measurements are very challenging and are only possible in a few cases. This provides considerable scope for indirect measurements including transfer reactions, mass measurements, beta-decay and gamma- ray spectroscopy. The latter technique, until recently largely neglected as an input in nuclear astrophysics analyses, has clear advantages in locating resonances with high energy precision and assisting in determining the spin and parity of resonances. Such information is very valuable in a complementary approach to indirect determinations of key reaction rates. © 2009 American Institute of Physics.

    J Wu, S Nishimura, G Lorusso, P Moller, E Ideguchi, Patrick Regan, GS Simpson, P-A Soderstrom, Philip Walker, H Watanabe, ZY Xu, H Baba, F Browne, R Daido, P Doornenbal, YF Fang, G Gey, T Isobe, PS Lee, JJ Liu, Z Li, Z Korkulu, Z Patel, V Phong, S Rice, H Sakurai, L Sinclair, T Sumikama, M Tanaka, A Yagi, YL Ye, R Yokoyama, GX Zhang, T Alharbi, N Aoi, FL Bello Garrote, G Benzoni, AM Bruce, RJ Carroll, KY Chae, Z Dombradi, A Estrade, A Gottardo, CJ Griffin, H Kanaoka, I Kojouharov, FG Kondev, S Kubono, N Kurz, I Kuti, S Lalkovski, GJ Lane, EJ Lee, T Lokotko, Gavin Lotay, C-B Moon, H Nishibata, I Nishizuka, CR Nita, A Odahara, Zsolt Podolyak, OJ Roberts, H Schaffner, Callum Shand, J Taprogge, S Terashima, Z Vajta, S Yoshida (2017)94 -Decay Half-lives of Neutron-Rich 55Cs to 67Ho: Experimental Feedback and Evaluation of the r-Process Rare-Earth Peak Formation, In: Physical Review Letters118(7)072701 American Physical Society

    The -decay half-lives of 94 neutron-rich nuclei 144−151Cs, 146−154Ba, 148−156La, 150−158Ce, 153−160Pr, 156−162Nd, 159−163Pm, 160−166Sm, 161−168Eu, 165−170Gd, 166−172Tb, 169−173Dy, 172−175Ho and two isomeric states 174mEr, 172mDy were measured at Radioactive Isotope Beam Factory (RIBF), providing a new experimental basis to test theoretical models. Striking, large drops of -decay half-lives are observed at neutron-number N = 97 for 58Ce, 59Pr, 60Nd, 62Sm, and N = 105 for 63Eu, 64Gd, 65Tb, 66Dy. Features in the data mirror the interplay between pairing effects and microscopic structure. r-Process network calculations performed for a range of mass models and astrophysical conditions show that the 57 half-lives measured for the first time play an important role in shaping the abundance pattern of rare-earth elements in the solar system.

    E Simmons, L Trache, A Banu, M McCleskey, B Roeder, A Spiridon, RE Tribble, T Davinson, PJ Woods, GJ Lotay, J Wallace, D Doherty, A Saastamoinen (2013)The beta-delayed proton and gamma decay of 27P for nuclear astrophysics, In: Journal of Physics: Conference Series420(1)

    The creation site of 26Al is still under debate. It is thought to be produced in hydrogen burning and in explosive helium burning in novae and supernovae, and possibly also in the H-burning in outer shells of red giant stars. Also, the reactions for its creation or destruction are not completely known. When 26Al is created in novae, the reaction chain is: 24Mg(p,γ)25AI(β+v)25 Mg(p,γ)26Al, but this chain can be by-passed by another chain, 25Al(p, γ)26Si(p, γ)27P and it can also be destroyed directly. The reaction 26m Al (p, γ) 27 Si* is another avenue to bypass the production of 26Al and it is dominated by resonant capture. We find and study these resonances by an indirect method, through the beta-decay of 27P. A clean and abundant source of 27P was produced for the first time and separated with MARS. A new implantation-decay station which allows increased efficiency for low energy protons and for high-energy gamma-rays was used. We measured gamma-rays and beta-delayed protons emitted from states above the proton threshold in the daughter nucleus 27Si to identify and characterize the resonances. The lifetime of 27P was also measured with accuracy under 2%.

    E Simmons, L Trache, A Banu, M McCleskey, B Roeder, A Spiridon, RE Tribble, A Saastamoinen, J Aysto, T Davinson, PJ Woods, GJ Lotay, J Wallace (2010)Very low energy protons from the beta decay of proton rich nuclei for nuclear astrophysics, In: AIP Conference Proceedings1304pp. 415-419 AIP Publishing

    The MARS group at TAMU has developed a new experimental technique to measure very low energy protons from β-delayed proton-decay of proton-rich nuclei produced and separated with the MARS recoil spectrometer at TAMU. Recently we have investigated the β-delayed p-decays of 23Al [1], and 31Cl [2], and obtained information on the resonances in the 22Na(p,γ)23Mg and 30P(p,γ) 31S reactions, respectively. These reactions are important in explosive H-burning in Novae [3]. Recently an experiment looking at the β-delayed p-decay of 20Mg was also done in order to obtain information on resonances in the 19Ne(p,γ)20Na reaction. A simple setup consisting of a telescope made of a thin double sided Si strip detector (p-detector) backed or sandwiched between two thick Si detectors (β-detectors) was designed. We studied different W1 and BB2 p-detectors made by MSL, and found that the thinner detectors with a small cell size are best to measure proton energies as low as 2-300 keV. © 2010 American Institute of Physics.

    CM Shand, E Wilson, Z Podolyak, H Grawe, BA Brown, B Fornal, RVF Janssens, M Bowry, M Bunce, MP Carpenter, RJ Carroll, CJ Chiara, N Cieplicka-Orynczak, AY Deo, GD Dracoulis, CR Hoffman, RS Kempley, FG Kondev, GJ Lane, T Lauritsen, G Lotay, MW Reed, PH Regan, C Rodriguez-Triguero, D Seweryniak, B Szpak, PM Walker, S Zhu (2015)STRUCTURE OF Pb-207 POPULATED IN Pb-208+Pb-208 DEEP-INELASTIC COLLISIONS, In: ACTA PHYSICA POLONICA B46(3)pp. 619-622 WYDAWNICTWO UNIWERSYTETU JAGIELLONSKIEGO

    The yrast structure of 207Pb above the 13=2+ isomeric state has been investigated in deep-inelastic collisions of 208Pb and 208Pb at ATLAS, Argonne National Laboratory. New and previously observed transitions were measured using the Gammasphere detector array. The level scheme of 207Pb is presented up to ∼ 6 MeV, built using coincidence and γ-ray intensity analyses. Spin and parity assignments of states were made, based on angular distributions and comparisons to shell model calculations.

    M Grieser, YA Litvinov, R Raabe, K Blaum, Y Blumenfeld, PA Butler, F Wenander, PJ Woods, M Aliotta, A Andreyev, A Artemyev, D Atanasov, T Aumann, D Balabanski, A Barzakh, L Batist, A-P Bernardes, D Bernhardt, J Billowes, S Bishop, M Borge, I Borzov, F Bosch, AJ Boston, C Brandau, W Catford, R Catherall, J Cederkäll, D Cullen, T Davinson, I Dillmann, C Dimopoulou, G Dracoulis, CE Düllmann, P Egelhof, A Estrade, D Fischer, K Flanagan, L Fraile, MA Fraser, SJ Freeman, H Geissel, J Gerl, P Greenlees, RE Grisenti, D Habs, R von Hahn, S Hagmann, M Hausmann, JJ He, M Heil, M Huyse, D Jenkins, A Jokinen, B Jonson, DT Joss, Y Kadi, N Kalantar-Nayestanaki, BP Kay, O Kiselev, H-J Kluge, M Kowalska, C Kozhuharov, S Kreim, T Kröll, J Kurcewicz, M Labiche, RC Lemmon, M Lestinsky, G Lotay, XW Ma, M Marta, J Meng, D Mücher, I Mukha, A Müller, AS Murphy, G Neyens, T Nilsson, C Nociforo, W Nörtershäuser, RD Page, M Pasini, N Petridis, N Pietralla, M Pfützner, Z Podolyák, P Regan, MW Reed, R Reifarth, P Reiter, R Repnow, K Riisager, B Rubio, MS Sanjari, DW Savin, C Scheidenberger, S Schippers, D Schneider, R Schuch, D Schwalm, L Schweikhard, D Shubina, E Siesling, H Simon, J Simpson, J Smith, K Sonnabend, M Steck, T Stora, T Stöhlker, B Sun, A Surzhykov, F Suzaki, O Tarasov, S Trotsenko, XL Tu, P Van Duppen, C Volpe, D Voulot, PM Walker, E Wildner, N Winckler, DFA Winters, A Wolf, HS Xu, A Yakushev, T Yamaguchi, YJ Yuan, YH Zhang, K Zuber (2012)Storage ring at HIE-ISOLDE: Technical design report: Technical design report, In: European Physical Journal: Special Topics207(1)pp. 1-117 EDP Sciences/Springer

    We propose to install a storage ring at an ISOL-type radioactive beam facility for the first time. Specifically, we intend to setup the heavy-ion, low-energy ring TSR at the HIE-ISOLDE facility in CERN, Geneva. Such a facility will provide a capability for experiments with stored secondary beams that is unique in the world. The envisaged physics programme is rich and varied, spanning from investigations of nuclear ground-state properties and reaction studies of astrophysical relevance, to investigations with highly-charged ions and pure isomeric beams. The TSR might also be employed for removal of isobaric contaminants from stored ion beams and for systematic studies within the neutrino beam programme. In addition to experiments performed using beams recirculating within the ring, cooled beams can also be extracted and exploited by external spectrometers for high-precision measurements. The existing TSR, which is presently in operation at the Max-Planck Institute for Nuclear Physics in Heidelberg, is well-suited and can be employed for this purpose. The physics cases as well as technical details of the existing ring facility and of the beam and infrastructure requirements at HIE-ISOLDE are discussed in the present technical design report.

    G Christian, Gavin Lotay, C Ruiz, C Akers, D Burke, Wilton Catford, A Chen, D Connolly, B Davids, J Fallis, U Hager, D Hutcheon, A Mahl, A Rojas, X Sun (2018)Direct measurement of astrophysically important resonances in 38K( p,γ )39Ca, In: Physical Review C97(2)025802 American Physical Society

    Background: Classical novae are cataclysmic nuclear explosions occurring when a white dwarf in a binary system accretes hydrogen-rich material from its companion star. Novae are partially responsible for the galactic synthesis of a variety of nuclides up to the calcium ( A ∼ 40 ) region of the nuclear chart. Although the structure and dynamics of novae are thought to be relatively well understood, the predicted abundances of elements near the nucleosynthesis endpoint, in particular Ar and Ca, appear to sometimes be in disagreement with astronomical observations of the spectra of nova ejecta. Purpose: One possible source of the discrepancies between model predictions and astronomical observations is nuclear reaction data. Most reaction rates near the nova endpoint are estimated only from statistical model calculations, which carry large uncertainties. For certain key reactions, these rate uncertainties translate into large uncertainties in nucleosynthesis predictions. In particular, the 38 K ( p , γ ) 39 Ca reaction has been identified as having a significant influence on Ar, K, and Ca production. In order to constrain the rate of this reaction, we have performed a direct measurement of the strengths of three candidate ℓ = 0 resonances within the Gamow window for nova burning, at 386 ± 10 keV, 515 ± 10 keV, and 689 ± 10 keV. Method: The experiment was performed in inverse kinematics using a beam of unstable 38 K impinged on a windowless hydrogen gas target. The 39 Ca recoils and prompt γ rays from 38 K ( p , γ ) 39 Ca reactions were detected in coincidence using a recoil mass separator and a bismuth-germanate scintillator array, respectively. Results: For the 689 keV resonance, we observed a clear recoil- γ coincidence signal and extracted resonance strength and energy values of 120 + 50 − 30 ( stat . ) + 20 − 60 ( sys . ) meV and 679 + 2 − 1 ( stat . ) ± 1 ( sys . ) keV , respectively. We also performed a singles analysis of the recoil data alone, extracting a resonance strength of 120 ± 20 ( stat . ) ± 15 ( sys . ) meV, consistent with the coincidence result. For the 386 keV and 515 keV resonances, we extract 90 % confidence level upper limits of 2.54 meV and 18.4 meV, respectively. Conclusions: We have established a new recommended 38 K ( p , γ ) 39 Ca rate based on experimental information, which reduces overall uncertainties near the peak temperatures of nova burning by a factor of ∼ 250 . Using the rate obtained in this work in model calculations of the hottest oxygen-neon novae reduces overall uncertainties on Ar, K, and Ca synthesis to factors of 15 or less in all cases.

    P-A Söderström, Philip Walker, J Wu, HL Liu, Patrick Regan, H Watanabe, P Doornenbal, Z Korkulu, P Lee, JJ Liu, G Lorusso, S Nishimura, VH Phong, T Sumikama, FR Xu, S Lalkovski, Gavin Lotay, Z Patel, Zsolt Podolyak, Callum Shand (2016)K-mixing in the doubly mid-shell nuclide 170Dy and the role of vibrational degeneracy, In: Physics Letters B762pp. 404-408 Elsevier

    A detailed study of the structure of the doubly mid-shell nucleus View the MathML source has been carried out, following isomeric and β decay. We have measured the yrast band up to the spin-parity Jπ=6+ state, the K=2γ -vibration band up to the 5+ state, a low-lying negative-parity band based on a 2− state that could be a candidate for the lowest energy octupole vibration state within this nucleus, and a candidate for the Kπ=6+ two quasi-particle isomer. This state was determined to have an excitation energy of 1643.91(23) keV and a half life of 0.99(4) μs, with a reduced hindrance for its decay to the ground-state band an order of magnitude lower than predicted by NpNn systematics. This is interpreted as being due to γ -vibrational mixing from a near degeneracy of the isomer and the 6+ state of the γ band. Furthermore, the parent nucleus 170Tb has been determined to have a half-life of View the MathML source s with a possible spin-parity of 2−.

    G.X. Zhang, H. Watanabe, G.D. Dracoulis, F.G. Kondev, G.J. Lane, P.H. Regan, P.-A. Söderström, P.M. Walker, K. Yoshida, H. Kanaoka, Z. Korkulu, P.S. Lee, J.J. Liu, S. Nishimura, J. Wu, A. Yagi, D.S. Ahn, T. Alharbi, H. Baba, F. Browne, A.M. Bruce, M.P. Carpenter, R.J. Carroll, K.Y. Chae, C.J. Chiara, Zs. Dombradi, P. Doornenbal, A. Estrade, N. Fukuda, C. Griffin, E. Ideguchi, N. Inabe, T. Isobe, S. Kanaya, I. Kojouharov, T. Kubo, S. Kubono, N. Kurz, I. Kuti, S. Lalkovski, T. Lauritsen, C.S. Lee, E.J. Lee, C.J. Lister, G. Lorusso, G. Lotay, E.A. McCutchan, C.-B. Moon, I. Nishizuka, C.R. Nita, A. Odahara, Z. Patel, V.H. Phong, Zs. Podolyak, O.J. Roberts, H. Sakurai, H. Schaffner, D. Seweryniak, C.M. Shand, Y. Shimizu, T. Sumikama, H. Suzuki, H. Takeda, S. Terashima, Zs. Vajta, J.J. Valiente-Dóbon, Z.Y. Xu, S. Zhu (2019)Interplay of quasiparticle and vibrational excitations: First observation of isomeric states in ¹⁶⁸Dy and ¹⁶⁹Dy, In: Physics Letters B799135036pp. 1-7 Elsevier

    The neutron-rich dysprosium isotopes ¹⁶⁸Dy₁₀₂ and ¹⁶⁹Dy₁₀₃ have been investigated using the EURICA γ-ray spectrometer, following production via in-flight fission of a high-intensity uranium beam in conjunction with isotope separation through the BigRIPS separator at RIBF in RIKEN Nishina Center. For ¹⁶⁸Dy, a previously unreported isomer with a half-life of 0.57(7) μs has been identified at an excitation energy of 1378 keV, and its presence affirmed independently using γ-γ-γ coincidence data taken with Gammasphere via two-proton transfer from an enriched ¹⁷⁰Er target performed at Argonne National Laboratory. This isomer is assigned Jπ = Kπ = (4⁻) based on the measured transition strengths, decay patterns, and the energy systematics for two-quasiparticle states in N = 102 isotones. The underlying mechanism of two-quasiparticle excitations in the doubly midshell region is discussed in comparison with the deformed QRPA and multi-quasiparticle calculations. In ¹⁶⁹Dy, the B(E2) value for the transition de-exciting the previously unreported Kπ = (1/2⁻) isomeric state at 166 keV to the Kπ = (5/2⁻) ground state is approximately two orders of magnitude larger than the E2 strength for the corresponding isomeric-decay transition in the N = 103 isotone ¹⁷³Yb, suggesting the presence of a significant γ-vibrational admixture with a dominant neutron one-quasiparticle component in the isomeric state.

    Ryan Wilkinson, Gavin Lotay, A. Lennarz, C. Ruiz, G. Christian, C. Akers, W. N. Catford, A. A. Chen, D. Connolly, B. Davids, D. A. Hutcheon, D. Jedrejcic, A. M. Laird, L. Martin, E. McNeice, J. Riley, M. Williams (2017)Direct Measurement of the Key Ec.m.=456 keV Resonance in the Astrophysical Ne19(p,γ)Na20 Reaction and Its Relevance for Explosive Binary Systems, In: Physical Review Letters119(24) American Physical Society

    We have performed a direct measurement of the 19Ne(p,γ)20Na reaction in inverse kinematics using a beam of radioactive 19Ne. The key astrophysical resonance in the 19Ne+p system has been definitely measured for the first time at Ec.m.=456+5−2  keV with an associated strength of 17+7−5  meV. The present results are in agreement with resonance strength upper limits set by previous direct measurements, as well as resonance energies inferred from precision (3He, t) charge exchange reactions. However, both the energy and strength of the 456 keV resonance disagree with a recent indirect study of the 19Ne(d, n)20Na reaction. In particular, the new 19Ne(p,γ)20Na reaction rate is found to be factors of ∼8 and ∼5 lower than the most recent evaluation over the temperature range of oxygen-neon novae and astrophysical x-ray bursts, respectively. Nevertheless, we find that the 19Ne(p,γ)20Na reaction is likely to proceed fast enough to significantly reduce the flux of 19F in nova ejecta and does not create a bottleneck in the breakout from the hot CNO cycles into the rp process.

    A. Matta, W. M. Catford, N. A. Orr, J. Henderson, P. Ruotsalainen, G. Hackman, A. B. Garnsworthy, F. Delaunay, R. Wilkinson, G. Lotay, Naofumi Tsunoda, Takaharu Otsuka, A. J. Knapton, G. C. Ball, N. Bernier, C. Burbadge, A. Chester, D. S. Cross, S. Cruz, C. Aa. Diget, T. Domingo, T. E. Drake, L. J. Evitts, F. H. Garcia, S. Hallam, E. MacConnachie, M. Moukaddam, D. Muecher, E. Padilla-Rodal, O. Paetkau, J. Park, J. L. Pore, U. Rizwan, J. Smallcombe, J. K. Smith, K. Starosta, C. E. Svensson, J. Williams, M. Williams (2019)Shell evolution approaching the N=20 island of inversion: Structure of ²⁹Mg, In: Physical Review C99044320 American Physical Society

    The island of inversion for neutron-rich nuclei in the vicinity of N=20 has become the testing ground par excellence for our understanding and modeling of shell evolution with isospin. In this context, the structure of the transitional nucleus ²⁹Mg is critical. The first quantitative measurements of the single-particle structure of ²⁹Mg are reported, using data from the d(²⁸Mg, p γ)²⁹Mg reaction. Two key states carrying significant ℓ=3 (f-wave) strength were identified at 2.40±0.10 (Jπ=5/2¯) and 4.28±0.04 MeV (7/2¯). New state-of-the-art shell-model calculations have been performed and the predictions are compared in detail with the experimental results. While the two lowest 7/2¯ levels are well described, the sharing of single-particle strength disagrees with experiment for both the 3/2¯ and 5/2¯ levels and there appear to be general problems with configurations involving the p3/2 neutron orbital and core-excited components. These conclusions are supported by an analysis of the neutron occupancies in the shell-model calculations.

    D Seweryniak, G Lotay, PJ Woods, MP Carpenter, CJ Chiara, HM David, T Davinson, C Hoffman, RVF Janssens, TL Khoo, T Lauritsen, CJ Lister, Z Liu, EA McCutchan, AM Rogers, WB Walters, S Zhu (2011)Nuclear structure studies along the proton dripline at ATLAS, In: AIP Conference Proceedings1409pp. 49-54

    Nuclei far from the line of stability are a focal point of contemporary nuclear physics. Nuclear structure studies along the proton dripline remain an important component of the scientific program at the ATLAS facility. The Gammasphere gamma-ray array and the Fragment Mass Analyzer offer the unprecedented sensitivity and selectivity required to study nuclei at and beyond the proton dripline. Recent results in proton decay studies, in-beam γ-ray spectroscopy around 100Sn and studies of proton resonances in light nuclei involved in the astrophysical hydrogen burning are presented. Future prospects in the context of planned and on-going upgrades of ATLAS and experimental apparatus are also briefly discussed. © 2011 American Institute of Physics.