Discovery of 34g,mCl(p,γ)35Ar resonances activated at classical nova temperatures

Background: The thermonuclear 34g,mCl(p,γ)35Ar reaction rates are unknown due to a lack of experimental nuclear physics data. Uncertainties in these rates translate to uncertainties in S34 production in models of classical novae on oxygen-neon white dwarfs. S34 abundances have the potential to aid in the classification of presolar grains. Purpose: Determine resonance energies for the 34g,mCl(p,γ)35Ar 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: Ar35 excited states were populated by the 36Ar(d,t)35Ar reaction at E(d)=22MeV and reaction products were momentum analyzed by a high resolution quadrupole-dipole-dipole-dipole (Q3D) magnetic spectrograph. Results: Seventeen new Ar35 levels have been detected at a statistically significant level in the region Ex≈5.9–6.7MeV (Er<800keV) 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 34g,mCl(p,γ)35Ar reaction rates will require further experiments.