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Background: $^{40}\mathrm{K}$ plays a significant role in the radiogenic heating of Earth-like exoplanets, which can affect the development of a habitable environment on their surfaces. The initial amount of $^{40}\mathrm{K}$ in the interior of these planets depends on the composition of the interstellar clouds from which they formed. Within this context, nuclear reactions that regulate the production of $^{40}\mathrm{K}$ during stellar evolution can play a critical role.Purpose: In this study, we constrain for the first time the astrophysical reaction rate of $^{40}\mathrm{K}(n,p)^{40}\mathrm{Ar}$, which is responsible for the destruction of $^{40}\mathrm{K}$ during stellar nucleosynthesis. We provide to the nuclear physics community high-resolution data on the cross section and angular distribution of the $^{40}\mathrm{Ar}(p,n)^{40}\mathrm{K}$ reaction. These are important to various applications involving $^{40}\mathrm{Ar}$. The associated reaction rate of the $^{40}\mathrm{Ar}(p,n)^{40}\mathrm{K}$ process addresses a reaction rate gap in the Joint Institute for Nuclear Astrophysics REACLIB database in the region of intermediate-mass isotopes.Methods: We performed differential cross-section measurements on the $^{40}\mathrm{Ar}(p,n)^{40}\mathrm{K}$ reaction, for six energies in the center-of-mass system between 3.2 and 4.0 MeV and various angles between ${0}^{\ensuremath{\circ}}$ and ${135}^{\ensuremath{\circ}}$. The experiment took place at the Edwards Accelerator Laboratory at Ohio University using the beam swinger target location and a standard neutron time-of-flight technique. We extracted total and partial cross sections by integrating the double differential cross sections we measured.Results: The total and partial cross sections varied with energy due to the contribution from isobaric analog states and Ericson type fluctuations. The energy-averaged neutron angular distributions were symmetrical relative to ${90}^{\ensuremath{\circ}}$. Based on the experimental data, local transmission coefficients were extracted and were used to calculate the astrophysical reaction rates of $^{40}\mathrm{Ar}(p,n)^{40}\mathrm{K}$ and $^{40}\mathrm{K}(n,p)^{40}\mathrm{Ar}$ reactions. The new rates were found to vary significantly from the theoretical rates in the REACLIB library. We implemented the new rates in network calculations to study nucleosynthesis via the slow neutron capture process, and we found that the produced abundance of $^{40}\mathrm{K}$ is reduced by up to 10% compared to calculations with the library rates. At the same time, the above result removes a significant portion of the previous theoretical uncertainty on the $^{40}\mathrm{K}$ yields from stellar evolution calculations.Conclusions: Our results support a destruction rate of $^{40}\mathrm{K}$ in massive stars via the $^{40}\mathrm{K}(n,p)^{40}\mathrm{Ar}$ reaction that is larger compared to previous estimates. The rate of $^{40}\mathrm{K}$ destruction via the $^{40}\mathrm{K}(n,p)^{40}\mathrm{Ar}$ reaction now has a dramatically reduced uncertainty based on our measurement. This result directly affects the predicted stellar yields of $^{40}\mathrm{K}$ from nucleosynthesis, which is a critical input parameter for the galactic chemical evolution models that are currently employed for the study of significant properties of exoplanets.

We have developed and tested an experimental technique for the measurement of low-energy (p,n) reactions in inverse kinematics relevant to nuclear astrophysics. The proposed setup is located at the ReA3 facility at the National Superconducting Cyclotron Laboratory. In the current approach, we operate the beam-transport line in ReA3 as a recoil separator while tagging the outgoing neutrons from the (p,n) reactions with the low-energy neutron detector array (LENDA). The developed technique was verified by using the $^{40}$Ar(p,n)$^{40}$K reaction as a probe. The results of the proof-of-principle experiment with the $^{40}$Ar beam show that cross-section measurements within an uncertainty of $\sim$25\% are feasible with count rates up to 7 counts/mb/pnA/s. In this article, we give a detailed description of the experimental setup, and present the analysis method and results from the test experiment. Future plans on using the technique in experiments with the separator for capture reactions (SECAR) that is currently being commissioned are also discussed., Comment: Submitted to NIMA. Revised manuscript after referees' first review

The Gamow-Teller strength distribution from ${}^{88}$Sr was extracted from a $(t,{}^{3}\text{He}+\gamma)$ experiment at 115 MeV/$u$ to constrain estimates for the electron-capture rates on nuclei around $N=50$, between and including $^{78}$Ni and $^{88}$Sr, which are important for the late evolution of core-collapse supernovae. The observed strength below an excitation energy of 8 MeV was consistent with zero and below 10 MeV amounted to $0.1\pm0.05$. Except for a very-weak transition that could come from the 2.231-MeV $1^{+}$ state, no $\gamma$ lines that could be associated with the decay of known $1^{+}$ states were identified. The derived electron-capture rate from the measured strength distribution is more than an order of magnitude smaller than rates based on the single-state approximation presently used in astrophysical simulations for most nuclei near $N=50$. Rates based on shell-model and quasiparticle random-phase approximation calculations that account for Pauli blocking and core-polarization effects provide better estimates than the single-state approximation, although a relatively strong transition to the first $1^{+}$ state in $^{88}$Rb is not observed in the data. Pauli unblocking effects due to high stellar temperatures could partially counter the low electron-capture rates. The new data serves as a zero-temperature benchmark for constraining models used to estimate such effects.

The ^{23}Al(p,γ)^{24}Si reaction is among the most important reactions driving the energy generation in type-I x-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The ^{23}Al(d,n) reaction was used to populate the astrophysically important states in ^{24}Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2_{2}^{+} and (4_{1}^{+},0_{2}^{+}) state in ^{24}Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

The ^{23}Al(p,γ)^{24}Si reaction is among the most important reactions driving the energy generation in type-I x-ray bursts. However, the present reaction-rate uncertainty limits constraints on neutron star properties that can be achieved with burst model-observation comparisons. Here, we present a novel technique for constraining this important reaction by combining the GRETINA array with the neutron detector LENDA coupled to the S800 spectrograph at the National Superconducting Cyclotron Laboratory. The ^{23}Al(d,n) reaction was used to populate the astrophysically important states in ^{24}Si. This enables a measurement in complete kinematics for extracting all relevant inputs necessary to calculate the reaction rate. For the first time, a predicted close-lying doublet of a 2_{2}^{+} and (4_{1}^{+},0_{2}^{+}) state in ^{24}Si was disentangled, finally resolving conflicting results from two previous measurements. Moreover, it was possible to extract spectroscopic factors using GRETINA and LENDA simultaneously. This new technique may be used to constrain other important reaction rates for various astrophysical scenarios.

The 24 Mg(d,p 0,1,2 ) reactions were investigated in the present work for E d,lab = 1300–2050 keV, at four backward detection angles, namely at 140°, 150°, 160° and 170°, suitable for NRA depth profiling studies. Differential cross-sections were obtained for the first three proton levels (p 0 , p 1 , p 2 ), using a variable energy step. The differential cross-section ratio of the nat Mg(d,d 0 ) reaction with respect to the Rutherford one was also measured at 140° and at 150°, for the same deuteron beam energy range. The results have been compared to data already existing in literature, and similarities, as well as discrepancies are being discussed and analyzed. The possible existence of previously unknown high-excitation levels in the compound nucleus 26 Al is also discussed. The obtained results have been validated through benchmarking runs in the same angular range, at two deuteron beam energies, using a thick, high-purity, highly-pressed magnesium oxide pellet as target.

Equilibrium charge state distributions of stable 60Ni, 59Co, and 63Cu beams passing through a 1 μm thick Mo foil were measured at beam energies of 1.84 MeV/u, 2.09 MeV/u, and 2.11 MeV/u respectively. A 1-D position sensitive Parallel Grid Avalanche Counter detector (PGAC) was used at the exit of a spectrograph magnet, enabling us to measure the intensity of several charge states simultaneously. The number of charge states measured for each beam constituted more than 99% of the total equilibrium charge state distribution for that element. Currently, little experimental data exists for equilibrium charge state distributions for heavy ions with 19 ≲ Z p , Z t ≲ 54 (Zp and Zt, are the projectile’s and target’s atomic numbers respectively). Hence the success of the semi-empirical models in predicting typical characteristics of equilibrium CSDs (mean charge states and distribution widths), has not been thoroughly tested at the energy region of interest. A number of semi-empirical models from the literature were evaluated in this study, regarding their ability to reproduce the characteristics of the measured charge state distributions. The evaluated models were selected from the literature based on whether they are suitable for the given range of atomic numbers and on their frequent use by the nuclear physics community. Finally, an attempt was made to combine model predictions for the mean charge state, the distribution width and the distribution shape, to come up with a more reliable model. We discuss this new “combinatorial” prescription and compare its results with our experimental data and with calculations using the other semi-empirical models studied in this work.

The accurate determination of deuteron depth profile presents a strong analyt- ical challenge for all the principal IBA (Ion Beam Analysis) techniques. As far as NRA (Nuclear Reaction Analysis) is concerned, the 2 H(d,p) reaction, seems to be a promising candidate, especially in the case of complex matrices, or for the study of deep-implanted deuteron layers. In the present work di erential cross-section values for the 2 H(d,p) re- action have been determined at 140 o , 160 o and 170 o , for Ed;lab=900-1600 keV, with an energy step of 50 keV, using a well-characterized, thin C:D target deposited on a polished Si wafer. The experimental results were analyzed using the R-matrix calculations code AZURE.