Experimental investigation of the ³⁰S(α, p) thermonuclear reaction in x-ray bursts

We performed the first measurement of ³⁰S_+α resonant elastic scattering to experimentally examine the ³⁰S(α, p) stellar reaction rate in type I x-ray bursts. These bursts are the most frequent thermonuclear explosions in the galaxy, resulting from thermonuclear runaway on the surface of accreting neutron star binaries. The ³⁰S(α, p) reaction plays a critical role in burst models, yet very little is known about the compound nucleus ³⁴Ar at these energies nor the reaction rate itself. We performed a measurement of alpha elastic scattering with a radioactive beam of ³⁰S to experimentally probe the entrance channel. Utilizing a gaseous active target system and silicon detector array, we extracted the excitation function from 1.8 to 5.5 MeV near 160° in the center-of-mass frame. The experimental data were analyzed with an R-Matrix calculation, and we discovered several new resonances and extracted their quantum properties (resonance energy, width, spin, and parity). Finally, we calculated the narrow resonant thermonuclear reaction rate of ³⁰S(α, p) for these new resonances.