Reactions on certain proton-rich, radioactive nuclei have been shown to have a significant influence on X-ray bursts. We provide an overview of two recent measurements of important X-ray burst ...reactions using in-flight radioactive ion beams from the RESOLUT facility at the J. D. Fox Superconducting Accelerator Laboratory at Florida State University. The 17F(d,n)18Ne reaction was measured, and Asymptotic Normalization Coefficients were extracted for bound states in 18Ne that determine the direct-capture cross section dominating the 17F(p,γ)18Ne reaction rate for T≲ 0.45 GK. Unbound resonant states were also studied, and the single-particle strength for the 4.523-MeV (3+) state was found to be consistent with previous results. The 19Ne(d,n)20Na proton transfer reaction was used to study resonances in the 19Ne(p,γ)20Na reaction. The most important 2.65-MeV state in 20Na was observed to decay by proton emission to both the ground and first-excited states in 19Ne, providing strong evidence for a 3+ spin assignment and indicating that proton capture on the thermally-populated first-excited state in 19Ne is an important contributor to the 19Ne(p,γ)20Na reaction rate.
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The 33Cl + proton fusion reaction is of significant interested in understanding stellar explosions known as ONe classical novae. A measurement was performed at Argonne National Laboratory to ...determine properties of excited states in 34Ar, the product of this reaction. The experiment employed the Gammasphere array and the Fragment Mass Analyzer in order to measure gamma rays in coincidence with the 34Ar reaction products, respectively, from fusion evaporation reactions. This information was used to better understand the 33Cl + proton stellar reaction rate.
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34.
Neutron-hole strength in N = 81 nuclei Howard, A. M.; Freeman, S. J.; Sharp, D. K. ...
Physical review. C,
03/2020, Volume:
101, Issue:
3
Journal Article
Peer reviewed
Open access
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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.
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36.
SABRE: The Silicon Array for Branching Ratio Experiments Good, E. C.; Sudarsan, B.; Macon, K. T. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
04/2021, Volume:
1003
Journal Article
Peer reviewed
Open access
The Silicon Array for Branching Ratio Experiments (SABRE) is an array of segmented silicon detectors used in conjunction with the Super-Enge Split-Pole Spectrograph (SE-SPS) located at the John D. ...Fox Accelerator Laboratory at Florida State University. SABRE is designed to detect charged-particle decays from excited states in nuclei populated via transfer reactions. These decay particles are detected in coincidence with the light reaction products from transfer reactions, which are detected at the focal plane of the SE-SPS. In doing so, branching ratios (i.e. the percentage of time the state decays via a specific type of charged-particle emission) can be measured. The SABRE design is an improvement over previous arrays, as it has higher angular coverage, lower energy thresholds, and can accept a higher data rate. Further, the full experimental setup has already been used to study several reactions of interest to nuclear structure and astrophysics.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
37.
Neutron-hole strength in N=81 nuclei Howard, A. M.; Freeman, Sean J.; Sharp, D. K. ...
Physical review. C,
03/2020, Volume:
101, Issue:
3
Journal Article
Peer reviewed
Open access
A systematic study of neutron-hole strength in the N = 81 nuclei 137Ba, 139Ce, 141Nd, and 143Sm is reported. The single-neutron removal reactions (p,d) and (3He,α) were measured at energies of 23 and ...34 MeV, respectively. Spectroscopic factors were extracted from measured cross sections through a distorted-wave Born approximation analysis and centroids of single-particle strength have been established. Here, the change in these centroid energies as a function of proton number have been compared to calculations of the monopole shift for the s1/2 and h11/2 orbitals, where the majority of the strength has been observed. Significant fragmentation of strength was observed for the d and g7/2 orbitals, particularly for the latter orbital which is deeply bound, with summed strengths that indicate a significant amount lies outside of the measured excitation energy range.
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The β-decay Paul trap is a linear radiofrequency-quadrupole ion trap that has been developed for precision β-decay studies. The design of the trap electrodes allows a variety of radiation detectors ...to surround the cloud of trapped ions. The momentum of the low-energy recoiling daughter nuclei following β decay is negligibly perturbed by scattering and is available for study. This advantageous property of traps allows the kinematics of particles that are difficult or even impossible to directly detect to be precisely reconstructed using conservation of energy and momentum. An ion-trap system offers several advantages over atom traps, such as higher trapping efficiencies and element-independent capabilities. The first precision experiment using this system is a measurement of β-decay angular correlations in the decay of 8Li performed by inferring the momentum of the neutrino from the kinematic shifts imparted to the breakup α particles. Many other β-decay studies that would benefit from a determination of the nuclear recoil can be performed with this system.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
A measurement of the α-β-νover ¯ angular correlation in the Gamow-Teller decay (8)Li→(8)Be(*)+νover ¯+β, (8)Be(*)→α+α has been performed using ions confined in a linear Paul trap surrounded by ...silicon detectors. The energy difference spectrum of the α particles emitted along and opposite the direction of the β particle is consistent with the standard model prediction and places a limit of 3.1% (95.5% confidence level) on any tensor contribution to the decay. From this result, the amplitude of any tensor component C(T) relative to that of the dominant axial-vector component C(A) of the electroweak interaction is limited to |C(T)/C(A)|<0.18 (95.5% confidence level). This experimental approach is facilitated by several favorable features of the (8)Li β decay and has different systematic effects than the previous β-νover ¯ correlation results for a pure Gamow-Teller transition obtained from studying (6)He β decay.
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