³⁰S(\(\alpha \), p) Thermonuclear Reaction Rate from Experimental Level Structure of ³⁴Ar

Abstract

Type I x-ray bursts are the most frequent thermonuclear explosions in the galaxy. Owing to their recurrence from known astronomical objects, burst morphology is extensively documented, and they are modeled very successfully as neutron-deficient, thermonuclear runaway on the surface of accreting neutron stars. While reaction networks include hundreds of isotopes and thousands of nuclear processes, only a small subset appear to play a pivotal role. One such reaction is the 30 S(α, p) reaction, which is believed to be a crucial link in the explosive helium burning which is responsible for the large energy flux. However, very little experimental information is available concerning the cross section itself, nor the 34 Ar compound nucleus at the relevant energies. We performed the first study of the entrance channel via 30 S alpha resonant elastic scattering using a state-of-the-art, low-energy, 30 S radioactive ion beam. The measurement was performed in inverse kinematics using a newlydeveloped active target. An R-matrix analysis of the excitation function reveals previously unknown resonances, including their quantum properties of spin, parity, width, and energy.