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The 30P(p,¿)31S reaction plays an important role in understanding the nucleosynthesis of A=30 nuclides in oxygen-neon novae. The Gaseous Detector with Germanium Tagging was used to measure 31Cl ß-delayed proton decay through the key Jp=3/2+, 260-keV resonance. The intensity I260ßp=8.3+1.2-0.9×10-6 represents the weakest ß-delayed, charged-particle emission ever measured below 400 keV, resulting in a proton branching ratio of Gp/G=2.5+0.4-0.3×10-4. By combining this measurement with shell-model calculations for G¿ and past work on other resonances, the total 30P(p,¿)31S rate has been determined with reduced uncertainty. The new rate has been used in hydrodynamic simulations to model the composition of nova ejecta, leading to a concrete prediction of 30Si:28Si excesses in presolar nova grains and the calibration of nuclear thermometers., Postprint (author's final draft)

The radionuclide22Na is a target of¿-ray astronomy searches, predicted to be produced during thermonuclearrunaways driving classical novae. The22Na(p,¿)23Mg reaction is the main destruction channel of22Na during anova, hence, its rate is needed to accurately predict the22Na yield. However, experimental determinations of theresonance strengths have led to inconsistent results. In this Rapid Communication, we report a measurementof the branching ratios of the23Alß-delayed protons as a probe of the key 204-keV (center-of-mass)22Na(p,¿)23Mg resonance strength. We report a factor of 5 lower branching ratio compared to the most recentliterature value. The variation in22Na yield due to nuclear data inconsistencies was assessed using a series ofhydrodynamic nova outburst simulations and has increased to a factor of 3.8, corresponding to a factor of˜2uncertainty in the maximum detectability distance. This is the first reported scientific measurement using theGaseous Detector with Germanium Tagging system., Postprint (published version)

Nucleosynthesis in classical novae on oxygen-neon white dwarfs is sensitive to the poorly constrained thermonuclear rate of the 30P(p,¿)31S reaction. In order to improve this situation, a variety of experiments have been performed over the past decade to determine the properties of proton unbound 31S levels up to an excitation energy of ˜6.7 MeV. Inconsistencies in the energies and Jp values for these levels have made it difficult to produce a useful 30P(p,¿)31S reaction rate based on experimental information. In the present work, we revisit a subset of published data on the structure of 31S in order to shed light on these problems. First, we present an alternative calibration of 31P(3He, t)31S spectra using newly available high-precision data in order to address discrepant 31S excitation energies. Second, we apply a similar method to a recently acquired 32S(d, t)31S spectrum. Third, for a different 31P(3He, t)31S experiment in which angular distributions were acquired, we present alternative fits to the experimental data in order to address discrepant 31S Jp values. Finally, we compare the Jp values from 31P(3He, t)31S to those reported from in beam ¿-ray spectroscopy experiments in order to search for potential resolutions to the inconsistencies. Overall, viable new solutions to some of the problems emerge, but other problems persist., Peer Reviewed, Postprint (author's final draft)

Background: The thermonuclear Cl-34g,Cl-m(p,gamma)Ar-35 reaction rates are unknown due to a lack of experimental nuclear physics data. Uncertainties in these rates translate to uncertainties in S-34 production in models of classical novae on oxygen-neon white dwarfs. S-34 abundances have the potential to aid in the classification of presolar grains.; Purpose: Determine resonance energies for the Cl-34g,Cl-m(p,gamma)Ar-35 reactions within the region of astrophysical interest for classical novae to a precision of a few keV as an essential first step toward constraining their thermonuclear reaction rates.; Method: Ar-35 excited states were populated by the Ar-36(d,t)Ar-35 reaction at E(d) = 22 MeV and reaction products were momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph.; Results: Seventeen new Ar-35 levels have been detected at a statistically significant level in the region E-x approximate to 5.9-6.7 MeV (E-r < 800 keV) and their excitation energies have been determined to typical uncertainties of 3 keV. The uncertainties for five previously known levels have also been reduced substantially. The measured level density was compared to those calculated using the WBMB Hamiltonian within the sd-pf model space.; Conclusions: Most of the resonances in the region of astrophysical interest have likely been discovered and their energies have been determined, but the resonance strengths are still unknown, and experimentally constraining the Cl-34g,Cl-m(p,gamma)Ar-35 reaction rates will require further experiments., Postprint (published version)