Recent simulations of classical novae on oxygen-neon white-dwarf stars indicate that the isotopic ratio 32 S/ 33 S has the potential to be a remarkable indicator of presolar grains of nova origin. The 33 S(p,γ ) 34 Cl reaction influences this ratio directly by destroying 33 S in novae. Additionally, β-delayed γ rays from the metastable state of 34 Cl (t 1/2 = 32 min) have been suggested to be potential nova observables. We have measured the branches for known 33 S(p,γ ) 34 Cl resonances that are activated at temperatures relevant to oxygen-neon novae. We provide the first reliable uncertainties on these branches and the first upper limits for several previously unmeasured branches.

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Explosive hydrogen burning is expected to occur in classical novae and type I x-ray bursts at temperatures up to 2 GK. Energy generation and nucleosynthesis in these events depend on the thermonuclear rates of radiative proton capture reactions involving unstable reactants. For example, the 19 Ne(p, γ) 20 Na, 23 Mg(p, γ) 24 Al, 27 Si(p, γ) 28 P, 31 S(p, γ) 32 Cl, and 35 Ar(p, γ) 36 K reaction rates are each expected to be dominated by one or two narrow, isolated resonances whose properties must be determined experimentally. First and foremost, the resonance energies must be known in order to approximate their contributions to the reaction rate and facilitate direct measurements with radioactive ion beams. By preparing thin ion implanted carbon foil targets at the University of Washington and measuring the 20 Ne(3 He,t) 20 Na, 24 Mg(3 He,t) 24 Al, 28 Si(3 He,t) 28 P, 32 S(3 He,t) 32 Cl, and 36 Ar(3 He,t) 36 K reactions on them at 32 MeV with the Munich Q3D spectrograph, we have measured the ground state masses of 20 Na, 24 Al, 28 P, and 32 Cl and excitation energies in 32 Cl and 36 K to precisions on the order of 1 keV. We discuss our improvements on the thermonuclear rates of the 23 Mg(p, γ) 24 Al and 35 Ar(p, γ) 36 K reactions.

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