arXiv subjects

A. Palmisano-Kyle

Publications and source records attributed to A. Palmisano-Kyle.

5 recordsLinked to original sources

arXiv2026

$l$-forbidden $\mathbf{M1}$ strengths near $^{100}$Sn from knockout reactions in Cd and Sn

Neutron knockout reactions on beams of $^{104,102}$Cd, and $^{104}$Sn are presented. States in the residual $^{103,101}$Cd and $^{103}$Sn nuclei are populated, including low-lying $7/2^+$ states of $νg_{7/2}$ character. These states have half-lives $\approx 400$ ps due to their low energy and hindered $B(M1; 7/2^+ \rightarrow 5/2^+)$ strengths. The excited-state half-lives were measured using their Doppler-shifted lineshapes, and the resulting $B(M1)$ strengths are compared to Valence Space In Medium Similarity Renormalization Group (VS-IMSRG) calculations. The VS-IMSRG calculations under-predict the $l$-forbidden $M1$ strengths in the $^{100}$Sn region, as well as in other regions of the nuclear chart near $^{40}$Ca and $^{208}$Pb.

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arXiv2026

$β$-decay Measurements Near the $N=40$ Island of Inversion to Quantify Cooling of Accreted Neutron Star Crusts

Understanding the thermal structure of the outer crust of accreting neutron stars is important to interpret astronomical X-ray observations. Ground-state to ground-state $β$-decay transitions of neutron-rich nuclei comprising the crust enable Urca neutrino cooling processes that affect this thermal structure. Here we constrain the ground-state to ground-state transition strengths for the decays of $^{57}$Sc, $^{57}$Ti, and $^{59}$Ti based on experimental data. The data were obtained by combining total absorption $γ$-spectroscopy data from the SuN detection system with $β$-delayed neutron emission data from the NERO detection system at Michigan State University's National Superconducting Cyclotron Laboratory. We find $\log ft=$5.8$^{+0.3}_{-0.2}$ and $\log ft=$5.34$^{+0.08}_{-0.24}$ for the decays of $^{57}$Ti and $^{59}$Ti, respectively, and find no evidence for ground-state feeding in the decay of $^{57}$Sc. The results indicate weaker transitions than predicted by theory and indicated by previous measurements, resulting in reduced efficiency of neutrino cooling in accreted neutron star crusts in systems that exhibit X-ray superbursts.

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arXiv2025

Constraining the Synthesis of the Lightest p Nucleus 74Se

We provide the first experimental cross section of the $^{73}\text{As}(p,γ)^{74}\text{Se}$ reaction to constrain one of the main destruction mechanisms of the p nucleus $^{74}\text{Se}$ in explosive stellar environments. The measurement was done using a radioactive $^{73}\text{As}$ beam at effective center-of-mass energies of 2.9 and 2.3 MeV/nucleon. Along with the total cross-section measurement, statistical properties of the $^{74}\text{Se}$ compound nucleus were extracted, constraining the reaction cross section in the upper Gamow window of the $γ$ process. The impact of the experimentally constrained reaction rate on $^{74}\text{Se}$ production in Type II supernovae was investigated through Monte Carlo one-zone network simulations. The results indicate that the overproduction of $^{74}$Se by Type II supernova models cannot be resolved by nuclear physics alone and point toward the need for a more detailed understanding of the astrophysical conditions of relevance for the $γ$ process.

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arXiv2024

Enhanced production of 60Fe in massive stars

Massive stars are a major source of chemical elements in the cosmos, ejecting freshly produced nuclei through winds and core-collapse supernova explosions into the interstellar medium. Among the material ejected, long lived radioisotopes, such as 60Fe (iron) and 26Al (aluminum), offer unique signs of active nucleosynthesis in our galaxy. There is a long-standing discrepancy between the observed 60Fe/26Al ratio by γ-ray telescopes and predictions from supernova models. This discrepancy has been attributed to uncertainties in the nuclear reaction networks producing 60Fe, and one reaction in particular, the neutron-capture on 59Fe. Here we present experimental results that provide a strong constraint on this reaction. We use these results to show that the production of 60Fe in massive stars is higher than previously thought, further increasing the discrepancy between observed and predicted 60Fe/26Al ratios. The persisting discrepancy can therefore not be attributed to nuclear uncertainties, and points to issues in massive-star models.

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arXiv2023

Cross Section Measurement of the $^{82}$Kr(p,$γ$)$^{83}$Rb Reaction in Inverse Kinematics

The total cross section of the $^{82}$Kr(p,$γ$)$^{83}$Rb reaction was measured for the first time at effective center-of-mass energies between 2.4 and 3.0 MeV, within the relevant Gamow window for the astrophysical $γ$ process. The experiment took place at the National Superconducting Cyclotron Laboratory at Michigan State University using the ReA facility. A $^{82}$Kr beam was directed onto a hydrogen gas cell located at the center of the Summing NaI(Tl) (SuN) detector. The obtained spectra were analyzed using the $γ$-summing technique and the extracted cross section was compared to standard statistical model calculations using the \textsc{non-smoker} and \textsc{talys} codes. The comparison indicates that standard statistical model calculations tend to overproduce the cross section of the $^{82}$Kr(p,$γ$)$^{83}$Rb reaction relative to the experimentally measured values. Furthermore, the experimental data was used to provide additional constraints on the nuclear level density and $γ$-ray strength function used in the statistical model calculations.

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