Dr Daniel Doherty

Senior Lecturer
PhD (Edinburgh), MPhys (Warwick)
+44 (0)1483 686802
17 BC 04

Academic and research departments

Experimental Nuclear Physics Group, Department of Physics.


University roles and responsibilities

  • Physics Undergraduate Board of Studies Chair
  • Foundation Year Liaison
  • Year 1 Laboratory Lead



    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.

    L Morrison, K Hadyńska-Klek, Zs Podolyák, D. T Doherty, L. P Gaffney, L Kaya, L Próchniak, J Samorajczyk-Pyśk, J Srebrny, T Berry, A Boukhari, M Brunet, R Canavan, R Catherall, S. J Colosimo, J. G Cubiss, H De Witte, Ch Fransen, E Giannopoulos, T Kröll, H Hess, N Lalović, B Marsh, Y. Martinez Palenzuela, P. J Napiorkowski, G O'Neill, J Pakarinen, J. P Ramos, P Reiter, J. A Rodriguez, D Rosiak, S Rothe, M Rudigier, M Siciliano, J Snäll, P Spagnoletti, S Thiel, N Warr, F Wenander, R Zidarova, ZSOLT PODOLYAK, M Zielińska (2020)Quadrupole deformation of Xe 130 measured in a Coulomb-excitation experiment, In: Physical Review. C102054304

    Low-lying states in the isotope Xe130 were populated in a Coulomb-excitation experiment performed at CERN's HIE-ISOLDE facility. The magnitudes and relative signs of seven E2 matrix elements and one M1 matrix element coupling five low-lying states in Xe130 were determined using the semiclassical coupled-channel Coulomb-excitation least-squares search code gosia. The diagonal E2 matrix elements of both the 21+ and 41+ states were extracted for the first time. The reduced transition strengths are in line with those obtained from previous measurements. Experimental results were compared with the general Bohr Hamiltonian with the microscopic input from mean-field theory utilizing universal nuclear energy density functional (UNEDF0), shell-model calculations using the GCN50:82 and SN100PN interactions, and simple phenomenological models (Davydov-Filippov and γ-soft). The extracted shape parameters indicate triaxial-prolate deformation in the ground-state band. In general, good agreement between theoretical predictions and experimental values was found, while neither phenomenological model was found to provide an adequate description of Xe130.

    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.

    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.

    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.

    D. T. Doherty, A. N. Andreyev, L. Canete, D. Seweryniak, TAO HUANG, P. J. Woods, J. Li, M.P. Carpenter, K Auranen, AD Ayangeakaa, BB Back, S. Bottoni, J. G. Cubiss, JL Harker, T Haylett, R. V. F. Janssens, DG Jenkins, F. G. Kondev, T. Lauritsen, C. Lederer-Woods, C. Mueller-Gatermann, D. Potterveld, W Reviol, G Savard, S Stolze, S. Zhu (2021)Solving the Puzzles of the Decay of the Heaviest Known Proton-Emitting Nucleus ¹⁸⁵Bi, In: Physical Review Letters127202501 American Physical Society

    Two long-standing puzzles in the decay of ¹⁸⁵Bi, the heaviest known proton-emitting nucleus are revisited. These are the nonobservation of the 9/2(-) state, which is the ground state of all heavier odd-A Bi isotopes, and the hindered nature of proton and alpha decays of its presumed 60-mu s 1/2(+) ground state. The ¹⁸⁵Bi nucleus has now been studied with the ⁹⁵Mo(⁹³Nb, 3n) reaction in complementary experiments using the Fragment Mass Analyzer and Argonne Gas-Filled Analyzer at Argonne National Laboratory's ATLAS facility. The experiments have established the existence of two states in ¹⁸⁵Bi; the short-lived T-1/2 = 2.8(-1.0)(+2.3) mu s, proton- and alpha-decaying ground state, and a 58(2)-mu s gamma-decaying isomer, the half-life of which was previously attributed to the ground state. The reassignment of the ground-state lifetime results in a proton-decay spectroscopic factor close to unity and represents the only known example of a ground-state proton decay to a daughter nucleus (¹⁸⁴Pb) with a major shell closure. The data also demonstrate that the ordering of low- and high-spin states in ¹⁸⁵Bi is reversed relative to the heavier odd-A Bi isotopes, with the intruder-based 1/2(+) configuration becoming the ground, similar to the lightest At nuclides.

    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.

    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.

    WEI ZHANG, A. N. Andreyev, Z Liu, D. Seweryniak, H-H Huang, ZHONG LI, JUERONG LI, C Guo, DANIEL THOMAS DOHERTY, A Barzakh, P Van Duppen, J. G. Cubiss, B. Andel, S. Antalic, M. Block, A. Bronis, M.P. Carpenter, P. Copp, B. Ding, Z. Favier, F. Giacoppo, TAO HUANG, X Yu, B. Kindler, F. G. Kondev, T. Lauritsen, Gang LI, B. Lommel, H.Y. Lu, M. Al Monthery, P. Mosat, Ying Niu, C. Raison, W Reviol, G Savard, S Stolze, G Wilson, HUIHAI WU, Z Wang, FR Xu, Q Zeng, X. H. Zhou (2022)First observation of a shape isomer and a low-lying strongly-coupled prolate band in neutron-deficient semi-magic 187Pb, In: Physics letters. B829137129 Elsevier B.V

    Prompt and delayed γ-ray spectroscopy of the neutron-deficient, semi-magic isotope 187Pb has been performed using the recoil-decay and isomer-decay tagging techniques at the Argonne Gas-Filled Analyzer. A new 5.15(15)-μs isomeric state at only 308 keV above the spherical 3/2− ground state is identified and classified as a shape isomer. A strongly-coupled band is observed on top of the isomer, which is nearly identical to the one built on the prolate 7/2−[514] Nilsson state in the isotone 185Hg. Based on this similarity and on the result of the potential-energy surface calculations, the new isomer in 187Pb is proposed to originate from the same configuration. The retarded character of the 308-keV (7/2−)→3/2gs− transition with a deduced B(E2)=5.6(2)×10−4 W.u. can be well explained by the significant difference between the prolate parent and spherical daughter configurations, leading to the shape isomerism. The excitation energy of the isomer is surprisingly low, being roughly half of the excitation energies of the known 0+ intruder bandheads in the neighboring 186,188Pb isotopes. The combined results of the present work and the previous α-decay and laser spectroscopy studies present evidence for triple shape coexistence at low energy in the negative-parity configurations of 187Pb, which is well reproduced by the potential-energy surface calculations.

    A Kankainen, P. J. Woods, D. T. Doherty, H.M Albers, M Albers, AD Ayangeakaa, M.P. Carpenter, C.J. Chiara, JL Harker, R. V. F. Janssens, C. Lederer-Woods, D. Seweryniak, F Strieder, S. Zhu (2021)Decay of the key 92-keV resonance in the ²⁵Mg(p,γ) reaction to the ground and isomeric states of the cosmic γ-ray emitter ²⁶Al, In: Physics Letters B813136033 Elsevier

    The 92-keV resonance in the 25Mg(p,γ)²⁶Al reaction plays a key role in the production of ²⁶Al at astrophysical burning temperatures of ≈100 MK in the Mg-Al cycle. However, the state can decay to feed either the ground, ²⁶ᵍAl, or isomeric state, ²⁶ᵐAl. It is the ground state that is critical as the source of cosmic γ rays. It is therefore important to precisely determine the ground-state branching fraction f0 of this resonance. Here we report on the identification of four γ-ray transitions from the 92-keV resonance, and determine the spin of the state and its ground-state branching fraction f₀=0.52(2)stat(6)syst. The f₀ value is the most precise reported to date, and at the lower end of the range of previously adopted values, implying a lower production rate of ²⁶gAl and its cosmic 1809-keV γ rays.

    M. Rocchini, D. T. Doherty, K. Hadynska-Klek, A Nannini, A. Goasduff, M. Zielinska, D Testov, TR Rodriguez, A Gargano, F. Nowacki, G. De Gregorio, H. Naidja, P Sona, J.J. Valiente-Dóbon, D Mengoni, PR John, D Bazzacco, G Benzoni, A. Boso, P Cocconi, M. Chiari, F. Galtarossa, G Jaworski, M Komorowska, N. Marchini, M. Matejska-Minda, B Melon, R Menegazzo, P Napiorkowski, DR Napoli, M. Ottanelli, A Perego, L Ramina, M. Rampazzo, F Recchia, S. Riccetto, D Rosso, M Siciliano (2021)Onset of triaxial deformation in ⁶⁶Zn and properties of its first excited 0⁺state studied by means of Coulomb excitation, In: Physical Review C103(1)014311pp. 014311-1-014311-20 American Physical Society

    The electromagnetic structure of ⁶⁶Zn at low excitation energy was investigated via low-energy Coulomb excitation at INFN Legnaro National Laboratories, using the Gamma Array of Legnaro Infn Laboratories for nuclEar spectrOscopy (GALILEO) gamma-ray spectrometer coupled to the SPIDER (Silicon PIe DEtectoR). A set of reduced E2, E3, and M1 matrix elements was extracted from the collected data using the GOSIA code, yielding 12 reduced transition probabilities between the low-spin states and the spectroscopic quadrupole moment of the 21⁺ state. The B(E2) values for transitions depopulating the 0(2)(+) state have been determined for the first time, allowing for the lifetime of this state to be deduced and, consequently, the ρ2 (E0; 02+ -> 01+) monopole transition strength to be extracted. In addition, the B(E3;31- -> 01+) value has been determined for the first time in a Coulomb excitation experiment. The obtained results resolve the existing discrepancies between literature lifetimes and demonstrate that ⁶⁶Zn cannot be described by using simple collective models. Therefore, new state-of-the-art beyond-mean-field and large-scale shell-model calculations were performed in order to interpret the structure of this nucleus. Both the experimental and theoretical results suggest that the triaxial degree of freedom has an important impact on electromagnetic properties of ⁶⁶Zn, while the unique features of the 02+ state indicate its distinct and rather isolated structure.

    TJB Gray, JM Allmond, R. V. F. Janssens, W. Korten, AE STUCHBERY, James L. N. Wood, AD Ayangeakaa, S. Bottoni, B Bucher, CM Campbell, M.P. Carpenter, HL Crawford, HM David, DANIEL THOMAS DOHERTY, P Fallon, M.T. Febbraro, A Galindo-Uribarri, C Gross, M Komorowska, F. G. Kondev, T. Lauritsen, AO Macchiavelli, P. Napiorkowsi, E Padilla-Rodal, SD Pain, W Reviol, DG Sarantites, G Savard, D. Seweryniak, Charley WU, CHUN HEI YU, S. Zhu (2022)E2 rotational invariants of 01 + and 21 + states for 106Cd: The emergence of collective rotation, In: Phys.Lett.B834137446

    The collective structure of 106 Cd is elucidated by multi-step Coulomb excitation of a 3.849 MeV/A beam of 106 Cd on a 1.1 mg/cm 2 208 Pb target using GRETINA-CHICO2 at ATLAS. Fourteen E2 matrix elements were obtained. The nucleus 106 Cd is a prime example of emergent collectivity that possesses a simple structure: it is free of complexity caused by shape coexistence and has a small, but collectively active number of valence nucleons. This work follows in a long and currently active quest to answer the fundamental question of the origin of nuclear collectivity and deformation, notably in the cadmium isotopes. The results are discussed in terms of phenomenological models, the shell model, and Kumar-Cline sums of E2 matrix elements. The 〈 02 + | | E2 | | 21 + 〉 matrix element is determined for the first time, providing a total, converged measure of the electric quadrupole strength, 〈 Q2 〉 , of the first-excited 21 + level relative to the 01 + ground state, which does not show an increase as expected of harmonic and anharmonic vibrations. Strong evidence for triaxial shapes in weakly collective nuclei is indicated; collective vibrations are excluded. This is contrary to the only other cadmium result of this kind in 114 Cd by C. Fahlander et al. (1988) [38], which is complicated by low-lying shape coexistence near midshell.

    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.

    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.

    K Wimmer, W. Korten, P Doornenbal, T Arici, P. Aguilera, A Algora, T Ando, H Baba, B Blank, A. Boso, SX Chen, A. Corsi, P Davies, G de Angelis, G De France, J-P Delaroche, D. T. Doherty, Doherty D T, J. Gerl, M Girod, R Gernhaeuser, DG Jenkins, S. Koyama, T. Motobayashi, S Nagamine, M. Niikura, A. Obertelli, J Libert, D. Lubos, TR Rodriguez, B Rubio, E. Sahin, T Saito, H Sakurai, L. Sinclair, D Steppenbeck, R. Taniuchi, R Wadsworth, M. Zielinska (2021)Shape Changes in the Mirror Nuclei ⁷⁰Kr and ⁷⁰Se, In: Physical Review Letters126072501 American Physical Society

    We studied the proton-rich Tz = -1 nucleus ⁷⁰Kr through inelastic scattering at intermediate energies in order to extract the reduced transition probability, B(E2; 0+ -> 2+). Comparison with the other members of the A = 70 isospin triplet, ⁷⁰Br and ⁷⁰Se, studied in the same experiment, shows a 3σ deviation from the expected linearity of the electromagnetic matrix elements as a function of Tz. At present, no established nuclear structure theory can describe this observed deviation quantitatively. This is the first violation of isospin symmetry at this level observed in the transition matrix elements. A heuristic approach may explain the anomaly by a shape change between the mirror nuclei ⁷⁰Kr and ⁷⁰Se contrary to the model predictions.

    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.

    L. Morrison, K. Hadyńska-Klȩk, Zs Podolyák, L.P. Gaffney, M. Zielińska, B.A. Brown, Zsolt Podolyak, H. Grawe, P.D. Stevenson, T. Berry, A. Boukhari, M. Brunet, R. Canavan, R. Catherall, J. Cederkäll, S.J. Colosimo, J.G. Cubiss, H. De Witte, D.T. Doherty, E. Giannopoulos, Ch Fransen, M. Górska, G. Georgiev, H. Hess, L. Kaya, T. Kröll, N. Lalović, B. Marsh, Y. Martinez Palenzuela, G. O'Neill, J. Pakarinen, J.P. Ramos, P. Reiter, J.A. Rodriguez, D. Rosiak, S. Rothe, M. Rudigier, M. Siciliano, E.C. Simpson, J. Snall, P. Spagnoletti, S. Thiel, N. Warr, F. Wenander, R. Zidarova (2023)Quadrupole and octupole collectivity in the semi-magic nucleus 80206Hg126, In: Physics Letters B838137675 Elsevier

    The first low-energy Coulomb-excitation measurement of the radioactive, semi-magic, two proton-hole nucleus 206Hg, was performed at CERN's recently-commissioned HIE-ISOLDE facility. Two γ rays depopulating low-lying states in 206Hg were observed. From the data, a reduced transition strength B(E2;21+→01+)=4.4(6) W.u was determined, the first such value for an N=126 nucleus south of 208Pb, which is found to be slightly lower than that predicted by shell-model calculations. In addition, a collective octupole state was identified at an excitation energy of 2705 keV, for which a reduced B(E3) transition probability of 30−13+10 W.u was extracted. These results are crucial for understanding both quadrupole and octupole collectivity in the vicinity of the heaviest doubly-magic nucleus 208Pb, and for benchmarking a number of theoretical approaches in this key region. This is of particular importance given the paucity of data on transition strengths in this region, which could be used, in principle, to test calculations relevant to the astrophysical r-process.

    GAVIN JAMES LOTAY, S. A. Gillespie, MARIE WILLIAMS, T Rauscher, M Alcorta, M Amthor, C. Andreoiu, D Baal, G. C. Ball, S. S Bhattacharjee, H Behnamian, V Bildstein, C. Burbadge, WILTON NEIL CATFORD, DANIEL THOMAS DOHERTY, N. E Esker, F. H. Garcia, A. B. Garnsworthy, G. Hackman, K Hudson, SAMUEL JAMES HALLAM, SHAHEEN JAZRAWI, E Kasanda, ADAM RUSSELL KENNINGTON, YOUNGCHAN KIM, A. Lennarz, R. S Lubna, C. R Natzke, N Nishimura, B Olaizola, Charlie Paxman, A Psaltis, C. E. Svensson, J Williams, B Wallis, D Yates, D Walter, Davids B (2021)First Direct Measurement of an Astrophysical p-Process Reaction Cross Section Using a Radioactive Ion Beam, In: Physical review letters127(11)pp. 1-112701 APS

    Physical Review Letters 127, 112701 (2021) We have performed the first direct measurement of the 83Rb(p,g) radiative capture reaction cross section in inverse kinematics using a radioactive beam of 83Rb at incident energies of 2.4 and 2.7 A MeV. The measured cross section at an effective relative kinetic energy of Ecm = 2.393 MeV, which lies within the relevant energy window for core collapse supernovae, is smaller than the prediction of statistical model calculations. This leads to the abundance of 84Sr produced in the astrophysical p process being higher than previously calculated. Moreover, the discrepancy of the present data with theoretical predictions indicates that further experimental investigation of p-process reactions involving unstable projectiles is clearly warranted.

    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.

    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.

    LAETITIA CANETE, GAVIN JAMES LOTAY, G. Christian, DANIEL THOMAS DOHERTY, WILTON NEIL CATFORD, SAMUEL JAMES HALLAM, D. Seweryniak, H.M Albers, S Almaraz-Calderon, E.A Bennett, M.P. Carpenter, C.J. Chiara, JP Greene, C Hoffman, R. V. F. Janssens, J Jose, A Kankainen, T. Lauritsen, S Ota, A. Matta, A Saastamoinen, Ryan Wilkinson, M. Moukaddam, S. Zhu (2021)New constraints on the Al 25 ( p , γ ) reaction and its influence on the flux of cosmic γ rays from classical nova explosions, In: Physical review. C104L022802 American Physical Society (APS)

    The astrophysical 25Al(p,γ) 26Si reaction represents one of the key remaining uncertainties in accurately modeling the abundance of radiogenic 26Al ejected from classical novae. Specifically, the strengths of key proton-unbound resonances in 26Si, that govern the rate of the 25Al(p,γ) reaction under explosive astrophysical conditions, remain unsettled. Here, we present a detailed spectroscopy study of the 26Si mirror nucleus 26Mg. We have measured the lifetime of the 3+, 6.125-MeV state in 26Mg to be 19(3) fs and provide compelling evidence for the existence of a 1– state in the T = 1, A = 26 system, indicating a previously unaccounted for ℓ = 1 resonance in the 25Al(p,γ) reaction. Using the presently measured lifetime, together with the assumption that the likely 1– state corresponds to a resonance in the 25Al + p system at 435.7(53) keV, we find considerable differences in the 25Al(p,γ) reaction rate compared to previous works. Furthermore, based on current nova models, we estimate that classical novae may be responsible for up to ≈ 15% of the observed galactic abundance of 26Al.

    S Ota, G Christian, W. N Catford, G Lotay, M Pignatari, J. A Tostevin, U Battino, E. A Bennett, S Dede, D. T Doherty, S Hallam, F Herwig, J Hooker, C Hunt, H Jayatissa, A Matta, M Moukaddam, E Rao, G. V Rogachev, A Saastamoinen, D Scriven, S Upadhyayula, R Wilkinson (2021)(6Li, d) and (6Li, t) reactions on 22Ne and implications for s-process nucleosynthesis, In: Physical Review C104055806 American Physical Society

    We studied α cluster states in 26Mg via the 22Ne(6Li,dγ)26Mg reaction in inverse kinematics at an energy of 7 MeV/nucleon. States between Ex = 4–14 MeV in 26Mg were populated and relative α spectroscopic factors were determined. Some of these states correspond to resonances in the Gamow window of the 22Ne(α,n)25Mg reaction, which is one of the main neutron sources in the astrophysical s-process. Using our new 22Ne(α,n)25Mg and 22Ne(α,γ)26Mg reaction rates, we performed new s-process calculations for massive stars and asymptotic giant branch stars and compared the resulting abundances with the abundances obtained using other 22Ne+α rates from the literature. We observe an impact on the s-process abundances up to a factor of three for intermediate-mass AGB stars and up to a factor of ten for massive stars. Additionally, states in 25Mg at Ex < 7.5 MeV are identified via the 22Ne(6Li,t)25Mg reaction for the first time. We present the (6Li, t) spectroscopic factors of these states and note similarities to the (d,p) reaction in terms of reaction selectivity.

    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.

    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.

    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 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%.

    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)
    Daniel Doherty, JM Allmond, RVF Janssens, W Korten, S Zhu, M Zielinska, DC Radford, AD Ayangeakaa, B Bucher, JC Batchelder, CW Beausang, C Campbell, MP Carpenter, D Cline, HL Crawford, HM David, JP Delaroche, C Dickerson, P Fallon, A Galindo-Uribarri, FG Kondev, JL Harker, AB Hayes, M Hendricks, P Humby, M Girod, CJ Gross, M Klintefjord, K Kolos, GJ Lane, T Lauritsen, J Libert, AO Macchiavelli, PJ Napiorkowski, E Padilla-Rodal, RC Pardo, W Reviol, DG Sarantites, G Savard, D Seweryniak, J Srebrny, R Varner, R Vondrasek, A Wiens, E Wilson, JL Wood, CY Wu (2017)Triaxiality near the 110Ru ground state from Coulomb excitation, In: Physics Letters B766pp. 334-338 Elsevier

    A multi-step Coulomb excitation measurement with the GRETINA and CHICO2 detector arrays was carried out with a 430-MeV beam of the neutron-rich 110Ru (t1/2=12s) isotope produced at the CARIBU facility. This represents the first successful measurement following the post-acceleration of an unstable isotope of a refractory element. The reduced transition probabilities obtained for levels near the ground state provide strong evidence for a triaxial shape; a conclusion confirmed by comparisons with the results of beyond-mean-field and triaxial rotor model calculations.

    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.

    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.

    JN Wilson, M Lebois, L Qi, P Amador-Celdran, D Bleuel, JA Briz, R Carroll, Wilton Catford, H De Witte, D Doherty, R Eloirdi, G Georgiev, A Gottardo, A Goasduff, K Hadynska-Klek, K Hauschild, M Hess, V Ingeberg, T Konstantinopoulos, J Ljungvall, A Lopez-Martens, G Lorusso, R Lozeva, R Lutter, P Marini, I Matea, T Materna, L Mathieu, A Oberstedt, S Oberstedt, S Panebianco, Zsolt Podolyak, D Porta, Patrick Regan, P Reiter, K Rezynkina, SJ Rose, E Sahin, M Seidlitz, Robert Shearman, B Siebeck, S Siem, AG Smith, GM Tveten, D Verney, N Warr, F Zeiser, M Zielinska (2017)PRODUCTION AND STUDY OF NEUTRON-RICH NUCLEI USING THE LICORNE DIRECTIONAL NEUTRON SOURCE, In: Acta Physica Polonica B48(3)pp. 395-401 Państwowe Wydawn. Naukowe

    We have recently successfully demonstrated a new technique for production and study of many of the most exotic neutron-rich nuclei at moderate spins. LICORNE, a newly developed directional inverse-kinematic fast neutron source at the IPN Orsay, was coupled to the MINIBALL high resolution -ray spectrometer to study nuclei the furthest from stability using the 238U(n; f) reaction. This reaction and 232Th(n; f) are the most neutron-rich fission production mechanisms achievable and can be used to simultaneously populate hundreds of neutron-rich nuclei up to spins of 16 ~. High selectivity in the experiment was achieved via triple -ray coincidences and the use of a 400 ns period pulsed neutron beam, a technique which is unavailable to other population mechanisms such as 235U(nth; f) and 252Cf(SF). The pulsing allows time correlations to be exploited to separate delayed rays from isomeric states in the hundreds of nuclei produced, which are then used to cleanly select a particular nucleus and its exotic binary partners. In the recent experiment, several physics cases are simultaneously addressed such as shape coexistence, the evolution of shell closures far from stability, and the spectroscopy of nuclei in the r-process path near N = 82. Preliminary physics results on anomalies in the 238U(n; f) fission yields and the structure of the 138Te and 100Sr nuclei will soon be published. A future project, -ball, to couple LICORNE with a hybrid escape-suppressed spectrometer to refine further the technique and achieve a large increase in the observational limit is discussed.

    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.

    W. Korten, A. Atac, D. Beaumel, P. Bednarczyk, M.A Bentley, G. Benzoni, A. Boston, A. Bracco, J. Cederkall, B. Cederwall, M. Ciemala, E. Clement, F .C. L. Crespi, D. Curien, G. de Angelis, F. Didierjean, D.T Doherty, Zs. Dombradi, G. Duchene, J. Dudek, B. Fernandez-Dominguez, B. Fornal, A. Gadea, L. P. Gaffney, J. Gerl, K. Gladnishki, A. Goasduff, M. Gorska, P.T Greenlees, H. Hess, D.G Jenkins, P. R. John, A. Jungclaus, M. Kmiecik, A. Korichi, M. Labiche, S. Leoni, J. Ljungvall, A. Lopez-Martens, A. Maj, D. Mengoni, B. Million, A. Nannini, D. Napoli, P.J Nolan, J. Nyberg, A. Obertelli, J. Pakarinen, N. Pietralla, Zsolt Podolyak, B. Quintana, R. Raabe, G. Rainovski, F. Recchia, P. Reiter, D. Rudolph, J. Simpson, Ch. Theisen, D. Tonev, A. Tumino, J.J Valiente-Dobon, O. Wieland, K. Wimmer, M. Zielinska (2020)Physics opportunities with the Advanced Gamma Tracking Array - AGATA, In: European Physical Journal A56(137) Springer Verlag

    New physics opportunities are opening up by the Advanced Gamma Tracking Array, AGATA,as it evolves to the full 4 instrument. AGATA is a high-resolution -ray spectrometer, solely built from highly segmented high-purity Ge detectors, capable of measuring rays from a few tens of keV to beyond 10 MeV, with unprecedented effciency, excellent position resolution for individual -ray interactions, and very high count-rate capability. As a travelling detector AGATA will be employed at all major current and near-future European research facilities delivering stable and radioactive ion beams.

    J. N. Wilson, M. Lebois, L. Qi, P. Amador-Celdran, D. Bleuel, J. A. Briz, R. Carroll, Wilton Catford, H. De Witte, D. T. Doherty, R. Eloirdi, G. Georgiev, A. Gottardo, A. Goasduff, K. Hadyńska-Klęk, K. Hauschild, H. Hess, V. Ingeberg, T. Konstantinopoulos, J. Ljungvall, A. Lopez-Martens, G. Lorusso, R. Lozeva, R. Lutter, P. Marini, I. Matea, T. Materna, L. Mathieu, A. Oberstedt, S. Oberstedt, S. Panebianco, Zsolt Podolyak, A. Porta, Patrick Regan, P. Reiter, K. Rezynkina, S. J. Rose, E. Sahin, M. Seidlitz, O. Serot, Robert Shearman, B. Siebeck, S. Siem, A. G. Smith, G. M. Tveten, D. Verney, N. Warr, F. Zeiser, M. Zielinska (2017)Anomalies in the Charge Yields of Fission Fragments from the U(n,f)238 Reaction, In: Physical Review Letters118(22)pp. 222501-1 American Physical Society

    Fast-neutron-induced fission of 238U at an energy just above the fission threshold is studied with a novel technique which involves the coupling of a high-efficiency γ-ray spectrometer (MINIBALL) to an inverse-kinematics neutron source (LICORNE) to extract charge yields of fission fragments via γ−γ coincidence spectroscopy. Experimental data and fission models are compared and found to be in reasonable agreement for many nuclei; however, significant discrepancies of up to 600% are observed, particularly for isotopes of Sn and Mo. This indicates that these models significantly overestimate the standard 1 fission mode and suggests that spherical shell effects in the nascent fission fragments are less important for low-energy fast-neutron-induced fission than for thermal neutron-induced fission. This has consequences for understanding and modeling the fission process, for experimental nuclear structure studies of the most neutron-rich nuclei, for future energy applications (e.g., Generation IV reactors which use fast-neutron spectra), and for the reactor antineutrino anomaly.

    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.

    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.

    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