Kankainen A, Woods P, Schatz H, Poxon-Pearson T, Doherty D, Bader V, Baugher T, Bazin D, Brown B, Browne J, Estrade A, Gade A, José J, Kontos A, Langer C, Lotay G, Meisel Z, Montes F, Noji S, Nunes F, Perdikakis G, Pereira J, Recchia F, Redpath T, Stroberg R, Scott M, Seweryniak D, Stevens J, Weisshaar D, Zegers R (2017) Measurement of key resonance states for the 30P(p, ³)31Sreaction rate, and the production of intermediate-mass elements in nova explosions, Physics Letters B 769 pp. 549-553
We report the first experimental constraints on spectroscopic factors and strengths of key resonances in the 30P(p, ³)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 ³-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 TH0.10?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.
Doherty DT, Allmond J, Janssens R, Korten W, Zhu S, Zielinska M, Radford D, Ayangeakaa A, Bucher B, Batchelder J, Beausang C, Campbell C, Carpenter M, Cline D, Crawford H, David H, Delaroche J, Dickerson C, Fallon P, Galindo-Uribarri A, Kondev F, Harker J, Hayes A, Hendricks M, Humby P, Girod M, Gross C, Klintefjord M, Kolos K, Lane G, Lauritsen T, Libert J, Macchiavelli A, Napiorkowski P, Padilla-Rodal E, Pardo R, Reviol W, Sarantites D, Savard G, Seweryniak D, Srebrny J, Varner R, Vondrasek R, Wiens A, Wilson E, Wood J, Wu C (2017) Triaxiality near the 110Ru ground state from Coulomb excitation, Physics Letters B 766 pp. 334-338
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.
Rudigier M., Canavan R.L., Regan P.H., Söderström P.-A., Lebois M., Wilson J.N., Jovancevic N., Bottoni S., Brunet M., Cieplicka-Orynczak N., Courtin S., Doherty D.T., Hadynska-Klek K., Heine M., Iskra W., Karayonchev V., Kennington A., Koseoglou P., Lotay G., Lorusso G., Nakhostin M., Nita C.R., S. Oberstedt S., Podolyak Zs., Qi L., Régis J.-M., Shearman R., Walker P.M., Witt W. (2019) Isomer spectroscopy and sub-nanosecond half-live determination in 178w using the NuBall array, Acta Physica Polonica B 50 (3) pp. 661-667
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.
Rudigier M., Walker P. M., Canavan R.L., Podolyak Zs., Regan P. H., Söderström P.-A., Lebois M., Wilson J.N., Jovancevic N., Blazhev A., Benito J., Bottoni S., Brunet M., Cieplicka-Orynczak N., Courtin S., Doherty D. T., Fraile L.M., Hadynska-Klek K., Heine M., Iskra A.W., Jolie J., Karayonchev V., Kennington A. R., Koseoglou P., Lotay G., Lorusso G., Nakhostin M., Nita C.R., Oberstedt S., Qi L., Régis J.-M., Sánchez-Tembleque V., Shearman R., Witt W., Vedia V., Zell K.O. (2020) Multi-quasiparticle sub-nanosecond isomers in 178W, Physics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics 801 135140
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.
Ota S., Christian G., Lotay G., Catford W.N, Bennett E.A, Dede S., Doherty Daniel, Hallam Sam, Hooker J., Hunt C., Jayatissa H., Matta A., Moukaddam Mohamad, Rogachev G.V, Saastamoinen A., Tostevin Jeffrey, Upadhyayula S., Wilkinson Ryan (2020) Decay properties of 22Ne + ý resonances and their impact
on s-process nucleosynthesis, Physics Letters B 802 135256
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(ý; n)25Mg reaction during the He-core and
C-shell burning phases of massive stars. This reaction, as well as the competing
22Ne(ý;)26Mg reaction, is not well constrained in the important temperature regime
from ý0:2?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
decay branching ratio of 1:14(26) for the key Ex = 11:32 MeV resonance in
26Mg, which results in a new (ý; n) strength for this resonance of 42(11) ýeV when
combined with the well-established (ý;
) strength of this resonance. We have also determined
new upper limits on the ý 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(ý; n)25Mg and 22Ne(ý;
)26Mg rates, which incorporate these results, indicate
that both rates are substantially lower than previously thought in the temperature range
from ý0:2?0:4 GK.