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Decay protons from excited states in $^{21}\mathrm{Na}$ populated through a previously reported $^{24}\mathrm{Mg}(p,\ensuremath{\alpha})^{21}\mathrm{Na}$ transfer reaction [Cha et al., Phys. Rev. C 96, 025810 (2017)] were analyzed to extract the proton branching ratios of the energy levels. By utilizing 31-MeV proton beams from the Holifield Radioactive Ion Beam Facility of Oak Ridge National Laboratory and isotopically enriched $^{24}\mathrm{Mg}$ solid targets, the decay protons were detected in coincidence with $\ensuremath{\alpha}$ particles from the $(p,\ensuremath{\alpha})$ reaction using a silicon strip detector array. Proton decay branching ratios of several $^{21}\mathrm{Na}$ levels were deduced for the $p0$ and $p1$ decay channels to the ground and first excited states in $^{20}\mathrm{Ne}$, respectively.

Due to its importance as an astronomical observable in core-collapse supernovae (CCSNe), the reactions producing and destroying $^{44}\mathrm{Ti}$ must be well constrained. Generally, statistical model calculations such as Hauser-Feshbach are employed when experimental cross sections are not available, but the variation in such adopted rates can be large. Here, data from the literature is compared with statistical model calculations of the $^{44}\mathrm{Ti}(\ensuremath{\alpha},p)^{47}\mathrm{V}$ reaction cross section and used to constrain the possible reaction rate variation over the temperatures relevant to CCSNe. Suggestions for targeted future measurements are given.

Precise antineutrino measurements are very sensitive to proper background characterization. We present an improved measurement of the $^{13}\mathrm{C}(\ensuremath{\alpha},n)^{16}\mathrm{O}$ reaction cross section which constitutes significant background for large $\overline{\ensuremath{\nu}}$ detectors. We greatly improve the precision and accuracy by utilizing a setup that is sensitive to the neutron energies while making measurements of the excited state transitions via secondary $\ensuremath{\gamma}$-ray detection. Our results shows a 54% reduction in the background contributions from the $^{16}\mathrm{O}({3}^{\ensuremath{-}},6.13\text{ }\mathrm{MeV})$ state used in the KamLAND analysis.

The $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ ground state cross section was measured for the first time using monoenergetic $\ensuremath{\gamma}$ rays with energies between 4.4 and 10 MeV at the High Intensity Gamma-ray Source. The reaction is important for the primordial Li problem and for testing our understanding of the mirror $\ensuremath{\alpha}$-capture reactions $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ and $^{3}\mathrm{He}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Be}$. Although over the last 30 years most measurements of the $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})^{7}\mathrm{Li}$ reaction have concentrated in an energy range below ${E}_{\ensuremath{\gamma}}=3.65$ MeV, measurements at higher energies could potentially restrict the extrapolation to astrophysically important energies. The experimental arrangement for measuring the $^{7}\mathrm{Li}(\ensuremath{\gamma},t)^{4}\mathrm{He}$ reaction included a large-area silicon detector array and several beam characterization instruments. The experimental astrophysical $S$ factor of $^{3}\mathrm{H}(\ensuremath{\alpha},\ensuremath{\gamma})$ calculated from the present data was fitted using the $R$-matrix formalism. The results are in disagreement with previous experimental measurements in the same energy range but the extrapolated $S$ factor agrees with the potential model calculation and lower energy experimental data.

Results are presented from the first neutron-transfer measurement on $^{80}\mathrm{Ge}$ using an exotic beam from the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory. Newly measured spins and spectroscopic factors of low-lying states of $^{81}\mathrm{Ge}$ are determined, and the neutron capture cross section on $^{80}\mathrm{Ge}$ was calculated in a direct-semidirect model to provide a more realistic ($n,\ensuremath{\gamma}$) reaction rate for $r$-process simulations. Furthermore, a region of shape coexistence around $N\ensuremath{\approx}50$ is confirmed and implications for the magic nature of $^{78}\mathrm{Ni}$ are discussed.

Background: The $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$ bottleneck reaction in Type I x-ray bursts is the most important thermonuclear reaction rate to constrain experimentally, to improve the accuracy of burst light-curve simulations. A proposed technique to determine the thermonuclear rate of this reaction employs the $^{20}\mathrm{Mg}(\ensuremath{\beta}p\ensuremath{\alpha})^{15}\mathrm{O}$ decay sequence. The key $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$ resonance at an excitation of 4.03 MeV is now known to be fed in $^{20}\mathrm{Mg}(\ensuremath{\beta}p\ensuremath{\gamma})^{19}\mathrm{Ne}$; however, the energies of the protons feeding the 4.03 MeV state are unknown. Knowledge of the proton energies will facilitate future $^{20}\mathrm{Mg}(\ensuremath{\beta}p\ensuremath{\alpha})^{15}\mathrm{O}$ measurements.Purpose: To determine the energy of the proton transition feeding the 4.03 MeV state in $^{19}\mathrm{Ne}$.Method: A fast beam of $^{20}\mathrm{Mg}$ was implanted into a plastic scintillator, which was used to detect $\ensuremath{\beta}$ particles. 16 high purity germanium detectors were used to detect $\ensuremath{\gamma}$ rays emitted following $\ensuremath{\beta}p$ decay. A Monte Carlo method was used to simulate the Doppler broadening of $^{19}\mathrm{Ne}\phantom{\rule{4pt}{0ex}}\ensuremath{\gamma}$-ray lines and compare to the experimental data.Results: The center of mass energy between the proton and $^{19}\mathrm{Ne}$, feeding the 4.03 MeV state, is measured to be $1.21{}_{\ensuremath{-}0.22}^{+0.25}\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$, corresponding to a $^{20}\mathrm{Na}$ excitation energy of $7.44{}_{\ensuremath{-}0.22}^{+0.25}\phantom{\rule{0.16em}{0ex}}\mathrm{MeV}$. Absolute feeding intensities and $\ensuremath{\gamma}$-decay branching ratios of $^{19}\mathrm{Ne}$ states were determined including the 1615 keV state, which has not been observed before in this decay. A new $\ensuremath{\gamma}$ decay branch from the 1536 keV state in $^{19}\mathrm{Ne}$ to the ground state is reported. The lifetime of the 1507 keV state in $^{19}\mathrm{Ne}$ is measured to be $4.3{}_{\ensuremath{-}1.1}^{+1.3}$ ps resolving discrepancies in the literature. Conflicting $^{20}\mathrm{Mg}(\ensuremath{\beta}p$) decay schemes in published literature are clarified.Conclusions: The utility of this Doppler broadening technique to provide information on $\ensuremath{\beta}$-delayed nucleon emission and excited-state lifetimes has been further demonstrated. In particular, knowledge of the proton energies feeding the 4.03 MeV $^{19}\mathrm{Ne}$ state in $^{20}\mathrm{Mg}\phantom{\rule{4pt}{0ex}}\ensuremath{\beta}$ decay will facilitate future measurements of the $\ensuremath{\alpha}$-particle branching ratio.

The astrophysical $S$-factor for the radiative proton capture reaction on $^7$Be ($S_{17}$) at low energies is affected by the $s$-wave scattering lengths. We report the measurement of elastic and inelastic scattering cross sections for the $^7$Be+p system in the center-of-mass energy range 0.474 - 2.740 MeV and center-of-mass angular range of 70$^\circ$- 150$^\circ$. A radioactive $^7$Be beam produced at Oak Ridge National Laboratory's (ORNL) Holifield Radioactive Ion Beam Facility was accelerated and bombarded a thin polypropylene (CH$_{2}$)$_\text n$ target. Scattered ions were detected in the segmented Silicon Detector Array. Using an $\textit{R}$-matrix analysis of ORNL and Louvain-la-Neuve cross section data, the $s$-wave scattering lengths for channel spins 1 and 2 were determined to be 17.34$^{+1.11}_{-1.33}$ and -3.18$^{+0.55}_{-0.50}$ fm, respectively. The uncertainty in the $s$-wave scattering lengths reported in this work is smaller by a factor of 5-8 compared to the previous measurement, which may reduce the overall uncertainty in $S_{17}$ at zero energy. The level structure of $^8$B is discussed based upon the results from this work. Evidence for the existence of 0$^+$ and 2$^+$ levels in $^8$B at 1.9 and 2.21 MeV, respectively, is observed.

Half of the elements heavier than iron are believed to be produced through the rapid neutron-capture process ($r$ process). The astrophysical environment(s) where the $r$ process occurs remains an open question, even after recent observations of neutron-star mergers and the associated kilonova. Features in the abundance pattern of $r$-process ashes may provide critical insight for distinguishing contributions from different possible sites, including neutron-star mergers and core-collapse supernovae. In particular, the largely unknown neutron-capture reaction rates on neutron-rich unstable nuclei near $^{132}\mathrm{Sn}$ could have a significant impact on the final $r$-process abundances. To better determine these neutron-capture rates, the $(d,p)$ reaction has been measured in inverse kinematics using radioactive ion beams of $^{126}\mathrm{Sn}$ and $^{128}\mathrm{Sn}$ and a stable beam of $^{124}\mathrm{Sn}$ interacting with a ${({\mathrm{CD}}_{2})}_{n}$ target. An array of position-sensitive silicon strip detectors, including the Super Oak Ridge Rutgers University Barrel Array, was used to detect light reaction products. In addition to the present measurements, previous measurements of $^{130,132}\mathrm{Sn}(d,p)$ were reanalyzed using state-of-the-art reaction theory to extract a consistent set of spectroscopic factors for $(d,p)$ reactions on even tin nuclei between the heaviest stable isotope $^{124}\mathrm{Sn}$ and doubly magic $^{132}\mathrm{Sn}$. The spectroscopic information was used to calculate direct-semidirect $(n,\ensuremath{\gamma})$ cross sections, which will serve as important input for $r$-process abundance calculations.

The $^{15}$O($\alpha$,$\gamma$)$^{19}$Ne reaction is responsible for breakout from the hot CNO cycle in Type I x-ray bursts. Understanding the properties of resonances between $E_x = 4$ and 5 MeV in $^{19}$Ne is crucial in the calculation of this reaction rate. The spins and parities of these states are well known, with the exception of the 4.14- and 4.20-MeV states, which have adopted spin-parities of 9/2$^-$ and 7/2$^-$, respectively. Gamma-ray transitions from these states were studied using triton-$\gamma$-$\gamma$ coincidences from the $^{19}$F($^{3}$He,$t\gamma$)$^{19}$Ne reaction measured with GODDESS (Gammasphere ORRUBA Dual Detectors for Experimental Structure Studies) at Argonne National Laboratory. The observed transitions from the 4.14- and 4.20-MeV states provide strong evidence that the $J^\pi$ values are actually 7/2$^-$ and 9/2$^-$, respectively. These assignments are consistent with the values in the $^{19}$F mirror nucleus and in contrast to previously accepted assignments.

In radioactive ion beam experiments, beams containing isomers can be of interest in probing nuclear structure and informing astrophysical reaction rates. While the production of mixed in-flight ground state and isomer beams using nucleon transfer can be generally understood through distorted wave Born approximation methodology, low-spin isomer production via fast fragmentation is relatively unstudied. To attain a practical understanding of low-spin isomer production using fast fragmentation beams, a test case of $^{38}\mathrm{K}/^{38m}\mathrm{K}$ was studied at the National Superconducting Cyclotron Laboratory's ReAccelerated Beam facility. Starting from lise++ predictions, the fragmentation momentum distribution was sampled to determine isomer production. In addition, the effects of the gas stopper gradient and charge breeding times were examined. In the case of $^{38}\mathrm{K}$, isomer production peaks at $\ensuremath{\sim}57%$. This maximum is observed just off the lise++ predicted optimum magnetic rigidity, with only small losses in beam intensity within a few percent of this optimum rigidity setting. Control of the isomer fraction was also achieved through the modification of charge breeding times. Fast fragmentation appears to be a feasible method for production of low-spin isomeric beams, but additional study is necessary to better describe the mechanism involved.

Background: $^{32}\mathrm{Cl}$ is a neutron-deficient isotope with a $\ensuremath{\beta}$-decay half-life of 298 ms and a spin and parity of ${J}^{\ensuremath{\pi}}={1}^{+}$. Previous measurements of $^{32}\mathrm{Cl} \ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays have yielded a $\ensuremath{\beta}$-decay scheme with twelve $\ensuremath{\beta}$-decay transitions, contributing to studies of nuclear structure and fundamental symmetries. Those experiments have been limited to the observation of $^{32}\mathrm{S}$ states with ${J}^{\ensuremath{\pi}}={0}^{+},{1}^{+},{2}^{+}$.Purpose: Our goal is to search for new $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays and $\ensuremath{\beta}$-decay transitions of $^{32}\mathrm{Cl}$ to $^{32}\mathrm{S}$.Methods: A measurement of $^{32}\mathrm{Cl} \ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ decay has been performed using the Clovershare array of high-purity germanium detectors at the National Superconducting Cyclotron Laboratory.Results: By acquiring the highest-statistics $^{32}\mathrm{Cl} \ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray spectrum to date and exploiting a new sensitivity to $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidences, this experiment has enabled the observation of nine previously unobserved $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray transitions, leading to the inference of five $\ensuremath{\beta}$-decay transitions never before observed in $^{32}\mathrm{Cl} \ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ decay. The set of observed states includes negative-parity states for the first time. By combining the new information with data from previous work, the lifetimes and partial widths of the 8861- and 9650-keV states of $^{32}\mathrm{S}$ have been determined. In addition, the $^{31}\mathrm{P}(p,\ensuremath{\alpha})\phantom{\rule{0.16em}{0ex}}^{28}\mathrm{Si}$ resonance strength of the 9650-keV state has been limited to $\ensuremath{\omega}\ensuremath{\gamma}l9.8$ meV, which is an improvement over direct measurements.Conclusion: An enhanced decay scheme has been constructed. Most of the excited bound $^{32}\mathrm{S}$ states that would correspond to allowed and first-forbidden $\ensuremath{\beta}$-decay transitions have been observed, demonstrating the potential of $\ensuremath{\beta}$-decay experiments to approach complete spectroscopy measurements at the next generation of radioactive beam facilities. The observed positive-parity levels are well matched by $sd$ shell-model calculations.

The Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target was used to perform spectroscopic studies of $^{20}\mathrm{Ne}+p$ reactions. Levels in $^{19}\mathrm{Ne}$ were probed via the $^{20}\mathrm{Ne}(p,d)^{19}\mathrm{Ne}$ reaction to constrain the astrophysical rate of the $^{18}\mathrm{F}(p,\ensuremath{\alpha})^{15}\mathrm{O}$ reaction. Additionally, the first spectroscopic study of the $^{20}\mathrm{Ne}(p,^{3}\mathrm{He})^{18}\mathrm{F}$ reaction was performed. Angular distribution data were used to determine or confirm the spins of several previously observed levels, and the existence of a strong subthreshold $^{18}\mathrm{F}(p,\ensuremath{\alpha})^{15}\mathrm{O}$ resonance was verified.

The $^{15}\mathrm{O}(\ensuremath{\alpha},\ensuremath{\gamma})^{19}\mathrm{Ne}$ reaction is expected to trigger the initial path for breakout from the CNO hydrogen-burning cycles to the rapid proton capture $(rp)$ process in type I x-ray bursts on accreting neutron stars. The thermonuclear reaction rate has a major impact on models of type I x-ray burst observables and it depends on the small $\ensuremath{\alpha}$-particle branching ratio, ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$, of the 4.03 MeV state in $^{19}\mathrm{Ne}$. Attempts to measure ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$ by populating the 4.03 MeV state using nuclear reactions have only led to strong upper limits. In the present work, we report the first experimental evidence that the 4.03 MeV $^{19}\mathrm{Ne}$ state is populated in $^{20}\mathrm{Mg} \ensuremath{\beta}$-delayed proton emission. This new channel has the potential to provide the necessary sensitivity to detect a finite value of ${\mathrm{\ensuremath{\Gamma}}}_{\ensuremath{\alpha}}/\mathrm{\ensuremath{\Gamma}}$.

The $^{24}\mathrm{Mg}(p,\ensuremath{\alpha})^{21}\mathrm{Na}$ reaction was measured at the Holifield Radioactive Ion Beam Facility of the Oak Ridge National Laboratory to study the spectroscopy of the radionuclide $^{21}\mathrm{Na}$. A 31-MeV proton beam from the 25 MV tandem accelerator bombarded isotopically enriched $^{24}\mathrm{Mg}$ targets. Recoiling $^{4}\mathrm{He}$ particles were identified by an annular silicon strip detector array. Two energy levels at ${E}_{x}=6.594$ and 7.132 MeV were observed for the first time. By comparing the experimentally obtained angular distributions and distorted wave Born approximation calculations, the spins and parities of $^{21}\mathrm{Na}$ energy levels were constrained. The astrophysically-important $^{17}\mathrm{F}(\ensuremath{\alpha},p)^{20}\mathrm{Ne}$ reaction rate was also calculated for the first time using resonance parameters for 12 energy levels.

We report the independent experimental confirmation of an isomeric state in the proton drip-line nucleus $^{26}$P. The ${\gamma}$-ray energy and half-life determined are 164.4 $\pm$ 0.3 (sys) $\pm$ 0.2 (stat) keV and 104 $\pm$ 14 ns, respectively, which are in agreement with the previously reported values. These values are used to set a semi-empirical limit on the proton separation energy of $^{26}$P, with the conclusion that it can be bound or unbound., Comment: 5 pages, 3 figures

Of particular interest in astrophysics is the $^{34}\mathrm{S}(p,\ensuremath{\gamma})^{35}\mathrm{Cl}$ reaction, which serves as a stepping stone in thermonuclear runaway reaction chains during a nova explosion. Though the isotopes involved are all stable, the reaction rate of this significant step is not well known, due to a lack of experimental spectroscopic information on states within the Gamow window above the proton separation threshold of $^{35}\mathrm{Cl}$. Measurements of level spins and parities provide input for the calculation of resonance strengths, which ultimately determine the astrophysical reaction rate of the $^{34}\mathrm{S}(p,\ensuremath{\gamma})^{35}\mathrm{Cl}$ proton capture reaction. By performing the $^{37}\mathrm{Cl}(p,t)^{35}\mathrm{Cl}$ reaction in normal kinematics at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory, we have conducted a study of the region of astrophysical interest in $^{35}\mathrm{Cl}$, and have made the first-ever constraint on the spin and parity assignment for a level at $6677\ifmmode\pm\else\textpm\fi{}15$ keV $({E}_{r}=306$ keV), inside the Gamow window for novae.

Background: Transfer reactions are a useful tool for studying nuclear structure, particularly in the regime of low level densities and strong single-particle strengths. In addition, transfer reactions can populate levels above particle decay thresholds, allowing for the possibility of studying the subsequent decays and furthering our understanding of the nuclei being probed. In particular, the decay of loosely bound nuclei such as $^{12}\mathrm{N}$ can help inform and improve structure models.Purpose: To learn about the decay of excited states in $^{12}\mathrm{N}$, to more generally inform nuclear structure models, particularly in the case of particle-unbound levels in low-mass systems which are within the reach of state-of-the-art ab initio calculations.Method: In this follow-up analysis of previously published data [Chipps et al. (JENSA Collaboration), Phys. Rev. C 92, 034325 (2015)], decay particles from excited states populated in $^{12}\mathrm{N}$ have been detected in coincidence with tritons from the $^{14}\mathrm{N}(p,t)^{12}\mathrm{N}$ transfer reaction. Specifically, decay protons from proton-unbound levels above $\ensuremath{\sim}2$ MeV excitation energy were observed by utilizing the Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas jet target.Results: Isotropic proton branching ratios for the $p0$ and $p1$ decay channels are calculated and decay particle spectra for the populated levels from $p0$, $p1$, and $p2$ decay are given.Conclusions: The current data from $^{14}\mathrm{N}(p,t)^{12}\mathrm{N}$ will help provide nuclear structure and decay information input to models in this mass region.

Background: Measurements of $\ensuremath{\beta}$ decay provide important nuclear structure information that can be used to probe isospin asymmetries and inform nuclear astrophysics studies.Purpose: To measure the $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ decay of $^{26}\text{P}$ and compare the results with previous experimental results and shell-model calculations.Method: A $^{26}\text{P}$ fast beam produced using nuclear fragmentation was implanted into a planar germanium detector. Its $\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$-ray emission was measured with an array of 16 high-purity germanium detectors. Positrons emitted in the decay were detected in coincidence to reduce the background.Results: The absolute intensities of $^{26}\text{P}\phantom{\rule{4.pt}{0ex}}\ensuremath{\beta}$-delayed $\ensuremath{\gamma}$ rays were determined. A total of six new $\ensuremath{\beta}$-decay branches and 15 new $\ensuremath{\gamma}$-ray lines have been observed for the first time in $^{26}\text{P}\phantom{\rule{4.pt}{0ex}}\ensuremath{\beta}$ decay. A complete $\ensuremath{\beta}$-decay scheme was built for the allowed transitions to bound excited states of $^{26}\text{Si}$. $ft$ values and Gamow-Teller strengths were also determined for these transitions and compared with shell-model calculations and the mirror $\ensuremath{\beta}$ decay of $^{26}\text{Na}$, revealing significant mirror asymmetries.Conclusions: A very good agreement with theoretical predictions based on the USDB shell model is observed. The significant mirror asymmetry observed for the transition to the first excited state $(\ensuremath{\delta}=51(10)%)$ may be evidence for a proton halo in $^{26}\text{P}$.

The thermonuclear ^{30}P(p,γ)^{31}S reaction rate is critical for modeling the final elemental and isotopic abundances of ONe nova nucleosynthesis, which affect the calibration of proposed nova thermometers and the identification of presolar nova grains, respectively. Unfortunately, the rate of this reaction is essentially unconstrained experimentally, because the strengths of key ^{31}S proton capture resonance states are not known, largely due to uncertainties in their spins and parities. Using the β decay of ^{31}Cl, we have observed the β-delayed γ decay of a ^{31}S state at E_{x}=6390.2(7) keV, with a ^{30}P(p,γ)^{31}S resonance energy of E_{r}=259.3(8) keV, in the middle of the ^{30}P(p,γ)^{31}S Gamow window for peak nova temperatures. This state exhibits isospin mixing with the nearby isobaric analog state at E_{x}=6279.0(6) keV, giving it an unambiguous spin and parity of 3/2^{+} and making it an important l=0 resonance for proton capture on ^{30}P.

$^{26}\mathrm{Al}$ remains an intriguing target for observational $\ensuremath{\gamma}$-ray astronomy, thanks to its characteristic decay. The $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction is the crucial link in a sequence that bypasses the production of the observable $^{26}\mathrm{Al}^{g}$ in favor of the short-lived isomeric state; determining its astrophysical reaction rate across a range of stellar environments has been the focus of many studies. A reanalysis of previous work, utilizing recent improvements in excitation energies and ground state masses, is presented to reduce the ambiguities in the literature and provide focus to future measurements.

As one of a series of physics cases to demonstrate the unique benefit of the new Jet Experiments in Nuclear Structure and Astrophysics (JENSA) gas-jet target for enabling next-generation transfer reaction studies, the $^{14}\mathrm{N}$ ($p, t$)$^{12}\mathrm{N}$ reaction was studied for the first time, using a pure jet of nitrogen, in an attempt to resolve conflicting information on the structure of $^{12}\mathrm{N}$. A potentially new level at 4.561-MeV excitation energy in $^{12}\mathrm{N}$ was found.

Background: The Doppler broadening of gamma-ray peaks is due to nuclear recoil from beta-delayed nucleon emission can be used to measure the energies of the nucleons. This method has never been tested using beta-delayed proton emission or applied to a recoil heavier than A = 10. Purpose: To test and apply this Doppler broadening method using gamma-ray peaks from the P-26(beta p gamma)Al-25 decay sequence. Methods: A fast beam of P-26 was implanted into a planar Ge detector, which was used as a P-26 beta-decay trigger. The SeGA array of high-purity Ge detectors was used to detect gamma rays from the P-26(beta p gamma)Al-25 decay sequence. Results: Radiative Doppler broadening in beta-delayed proton-gamma decay was observed for the first time. Moreover, the Doppler broadening analysis method was verified using the 1613-keV gamma-ray line for which the proton energies were previously known. The 1776-keV gamma ray de-exciting the 2720 keV Al-25 level was observed in P-26(beta p gamma)Al-25 decay for the first time and used to determine that the center-of-mass energy of the proton emission feeding the 2720-keV level is 5.1 +/- 1.0 (stat.) +/- 0.6 (syst.) MeV, corresponding to a Si-26 excitation energy of 13.3 +/- 1.0 (stat.) +/- 0.6more » (syst.) MeV for the proton-emitting level. Conclusions: Finally, the Doppler broadening method has been demonstrated to provide practical measurements of the energies for beta-delayed nucleon emissions populating excited states of nuclear recoils at least as heavy as A = 25.« less

The Galactic 1.809-MeV $\ensuremath{\gamma}$-ray signature from the $\ensuremath{\beta}$ decay of $^{26g}\mathrm{Al}$ is a dominant target of $\ensuremath{\gamma}$-ray astronomy, of which a significant component is understood to originate from massive stars. The $^{26g}\mathrm{Al}(p,\ensuremath{\gamma})^{27}\mathrm{Si}$ reaction is a major destruction pathway for $^{26g}\mathrm{Al}$ at stellar temperatures, but the reaction rate is poorly constrained due to uncertainties in the strengths of low-lying resonances in $^{27}\mathrm{Si}$. The $^{26g}\mathrm{Al}(d,p)^{27}\mathrm{Al}$ reaction has been employed in inverse kinematics to determine the spectroscopic factors, and hence resonance strengths, of proton resonances in $^{27}\mathrm{Si}$ via mirror symmetry. The strength of the 127-keV resonance is found to be a factor of 4 higher than the previously adopted upper limit, and the upper limit for the 68-keV resonance has been reduced by an order of magnitude, considerably constraining the $^{26g}\mathrm{Al}$ destruction rate at stellar temperatures.

The $\ensuremath{\alpha}(^{10}\mathrm{Be},\phantom{\rule{0.16em}{0ex}}\ensuremath{\alpha})^{10}\mathrm{Be}$ resonant scattering reaction has been measured at nine $^{10}\mathrm{Be}$ beam energies from 25 to 48 MeV, scanning out resonances in $^{14}\mathrm{C}$ from excitation energies of 13 to 24 MeV. Angular distribution measurements were used to assign the spin and parity of ${5}^{\ensuremath{-}}$ to resonances at ${E}_{x}=18.82(2)$ and 19.67(2) MeV and ${6}^{+}$ at ${E}_{x}=20.80(2)$ MeV. The data also strongly indicate a ${3}^{\ensuremath{-}}$ resonance at 17.32(2) MeV. The systematic uncertainty on the excitation energies is 175 keV. An $R$-matrix analysis has been performed for the excitation energy range 16.5 to 22 MeV. The data are discussed in terms of cluster bands in $^{14}\mathrm{C}$.

Classical novae are expected to contribute to the 1809-keV Galactic $\ensuremath{\gamma}$-ray emission by producing its precursor $^{26}\mathrm{Al}$, but the yield depends on the thermonuclear rate of the unmeasured $^{25}\mathrm{Al}(p,\ensuremath{\gamma})^{26}\mathrm{Si}$ reaction. Using the $\ensuremath{\beta}$ decay of $^{26}\mathrm{P}$ to populate the key ${J}^{\ensuremath{\pi}}={3}^{+}$ resonance in this reaction, we report the first evidence for the observation of its exit channel via a $1741.6\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{syst})\text{ }\text{ }\mathrm{keV}$ primary $\ensuremath{\gamma}$ ray, where the uncertainties are statistical and systematic, respectively. By combining the measured $\ensuremath{\gamma}$-ray energy and intensity with other experimental data on $^{26}\mathrm{Si}$, we find the center-of-mass energy and strength of the resonance to be ${E}_{r}=414.9\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{stat})\ifmmode\pm\else\textpm\fi{}0.3(\mathrm{syst})\ifmmode\pm\else\textpm\fi{}0.6(\mathrm{lit}.)\text{ }\text{ }\mathrm{keV}$ and $\ensuremath{\omega}\ensuremath{\gamma}=23\ifmmode\pm\else\textpm\fi{}6(\mathrm{stat}{)}_{\ensuremath{-}10}^{+11}(\mathrm{lit}.)\text{ }\text{ }\mathrm{meV}$, respectively, where the last uncertainties are from adopted literature data. We use hydrodynamic nova simulations to model $^{26}\mathrm{Al}$ production showing that these measurements effectively eliminate the dominant experimental nuclear-physics uncertainty and we estimate that novae may contribute up to 30% of the Galactic $^{26}\mathrm{Al}$.

Recent calculations suggest that the rate of neutron capture by 130Sn has a significant impact on late-time nucleosynthesis in the r-process. Direct capture into low-lying bound states is expected to be significant in neutron capture near the N=82 closed shell, so r- process reaction rates may be strongly impacted by the properties of neutron single particle states in this region. In order to investigate these properties, the (d, p) reaction has been studied in inverse kinematics using a 630 MeV beam of 130Sn (4.8 MeV/u) and a (CD2)n target. An array of Si strip detectors, including SIDAR and an early implementation of the ORRUBA, was used to detect reaction products. Results for the 130Sn(d, p)131Sn reaction are found to be very similar to those from the previously reported 132Sn(d, p)133Sn reaction. Direct-semidirect (n, ) cross section calculations, based for the first time on experimental data, are presented. The uncertainties in these cross sections are thus reduced by orders of magnitude from previous estimates.

The 28Si(p,3 He)26Al reaction was utilized for the first time to study the levels in 26Al, using a proton beam from the Holifield Radioactive Ion Beam Facility. Five previously unreported states in 26Al are observed and discussed, including Distorted Wave Born Approximation analysis. Proton-decay branching ratios consistent with previous studies and theoretical expectations were found by detecting decay protons from highly excited 26Al states in coincidence with the 3He particles.

Galactic 26Al is the first radioactive nucleus to be positively identified by -ray astronomy with detection of the 1.809 MeV ray associated with its decay. This nucleus is destroyed in astrophysical environments in the 26Al(p, )27Si and inelastic 26Al+p scattering reactions where properties of 27Si levels determine reaction rates. To investigate these properties, elastic and inelastic 26Al+p scattering reactions were measured between Ec.m. = 0.5 1.5 MeV at the Holifield Radioactive Ion Beam Facility (HRIBF) at Oak Ridge National Laboratory (ORNL). A candidate for a new resonance in the 26Al(p, )27Si reaction was identified. Upper limits were also set on the strengths of postulated resonances and on the cross section of the inelastic reaction, but there is little effect on current reaction rate calculations.

A recent discussion of theoretical work on the ${}^{25}$Al($p,\ensuremath{\gamma}$)${}^{26}$Si astrophysical reaction rate [W.A. Richter, B. Alex Brown, A. Signoracci and M. Wiescher, Phys. Rev. C 83, 065803 (2011)] omits some current and relevant experimental information in forming its scientific conclusions. Accounting for this new information has the potential to significantly alter the reaction rate derived in the paper.

Several resonances in $^{25}\mathrm{Al}$($p,\ensuremath{\gamma}$)$^{26}\mathrm{Si}$ have been studied via the $^{28}\mathrm{Si}$($p,t$)$^{26}\mathrm{Si}$ reaction. Triton energies and angular distributions were measured using a segmented annular detector array. An additional silicon detector array was used to simultaneously detect the coincident protons emitted from the decay of states in $^{26}\mathrm{Si}$ above the proton threshold in order to determine branching ratios. A resonance at $5927\ifmmode\pm\else\textpm\fi{}4$ keV has been experimentally confirmed as the first $\ensuremath{\ell}=0$ state above the proton threshold, with a proton branching ratio consistent with one.

The level structure of 22Na has been studied at the Holifield Radioactive Ion Beam Facility in Oak Ridge National Laboratory using the 24Mg(p,3He)22Na reaction. 41 and 41.5 MeV proton beams were generated by 25 MV tandem accelerator and bombarded isotopically enriched 24Mg targets. Angular distributions of recoiling 3He particles were extracted by using a segmented annular silicon strip detector array. Spins and parities for ten levels were constrained through a distorted wave Born approximation analysis of angular distributions including three above the proton threshold at 6.739 MeV.

We directly measure the {sup 17}F(p,{gamma}){sup 18}Ne resonant reaction using a mixed beam of {sup 17}F and {sup 17}O at the Holifield Radioactive Ion Beam Facility at Oak Ridge National Laboratory (ORNL). The astrophysically important 3{sup +} resonance at {approx}600 keV above the proton threshold in {sup 18}Ne is found to have a partial width {Gamma}{sub {gamma}} = 56 {+-} 24(stat) {+-} 30(sys) meV, in reasonable agreement with the theoretically predicted width. A 2{sigma} upper limit on the direct capture of S(E) = 65 keV b is determined at an energy of 800 keV. Experimental techniques and astrophysical implications are discussed.

The {sup 18}Ne({alpha},p){sup 21}Na reaction plays a crucial role in the ({alpha},p) process, which leads to the rapid proton capture process in x-ray bursts. The reaction rate depends upon properties of {sup 22}Mg levels above the {alpha} threshold at 8.14 MeV. Despite recent studies of these levels, only the excitation energies are known for most with no constraints on the spins. We have studied the {sup 24}Mg(p,t){sup 22}Mg reaction at the Oak Ridge National Laboratory (ORNL) Holifield Radioactive Ion Beam Facility (HRIBF), and by measuring the angular distributions of outgoing tritons, we provide some of the first experimental constraints on the spins of astrophysically important {sup 18}Ne({alpha},p){sup 21}Na resonances.

The rate of the (17)F(p,gamma)(18)Ne reaction is important in various astrophysical events. A previous (17)F(p,p)(17)F measurement identified a 3;{+} state providing the strongest resonance contribution, but the resonance strength was unknown. We have directly measured the (17)F(p,gamma)(18)Ne reaction using a mixed beam of (17)F and (17)O at ORNL. The resonance strength for the 3;{+} resonance in (18)Ne was found to be omegagamma = 33 +/- 14(stat) +/-1 7(syst) meV, corresponding to a gamma width of Gamma_{gamma} = 56 +/- 24(stat) +/- 30(syst) meV. An upper limit on the direct capture of S(E)

The magnitude of the {sup 15}N(n,{gamma}){sup 16}N reaction rate in asymptotic giant branch stars depends directly on the neutron spectroscopic factors of low-lying {sup 16}N levels. A new study of the {sup 15}N(d,p){sup 16}N reaction is reported populating the ground and first three excited states in {sup 16}N. The measured spectroscopic factors are near unity as expected from shell model calculations, resolving a long-standing discrepancy with earlier measurements that had never been confirmed or understood. Updated {sup 15}N(n,{gamma}){sup 16}N reaction rates are presented.

We have developed a novel technique for measurements of low-energy $(p,\ensuremath{\alpha})$ reactions using heavy-ion beams and a differentially pumped windowless gas target. We applied this new approach to study the 183 keV resonance in the $^{17}\mathrm{O}$($p,\ensuremath{\alpha}$)$^{14}\mathrm{N}$ reaction. We report a (center-of-mass) resonance energy of ${E}_{r}=183.5\genfrac{}{}{0}{}{+0.1}{\ensuremath{-}0.4}$ keV and a resonance strength of $\ensuremath{\omega}{\ensuremath{\gamma}}_{p\ensuremath{\alpha}}=(1.70\ifmmode\pm\else\textpm\fi{}0.15)$ meV, and we set an upper limit (95% confidence) on the total width of the state of $\ensuremath{\Gamma}l0.1$ keV. This resonance is important for the $^{17}\mathrm{O}$($p,\ensuremath{\alpha}$)$^{14}\mathrm{N}$ reaction rate, and we find that $^{18}\mathrm{F}$ production is significantly decreased in low-mass ONeMg novae but less affected in more energetic novae. We also report the first determination of the stopping power for oxygen ions in hydrogen gas near the peak of the Bragg curve ($E=193$ keV/u) to be $(63\ifmmode\pm\else\textpm\fi{}1)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$ eV cm${}^{2}$.