Spins and Parities of Astrophysically Importants30states Fromsi28…

The structure of proton-unbound $^{30}\mathrm{S}$ states strongly determines the thermonuclear $^{29}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{30}\mathrm{S}$ reaction rate at temperatures characteristic of explosive hydrogen burning in classical novae and type I x-ray bursts. Specifically, the rate had been previously predicted to be dominated by two low-lying, unobserved, levels in the ${E}_{x}=$ 4.7--4.8 MeV region, with spin and parity assignments of 3${}^{+}$ and 2${}^{+}$. In recent experimental work, two candidate levels were observed with energies of 4.699 MeV and 4.814 MeV, but no experimental information on their spins and parities was obtained. We have performed an in-beam $\ensuremath{\gamma}$-ray spectroscopy study of $^{30}\mathrm{S}$ with the $^{28}\mathrm{Si}$($^{3}\mathrm{He}$, $n\ensuremath{\gamma}$)$^{30}\mathrm{S}$ reaction. By constructing the decay schemes of proton-unbound states with a $\ensuremath{\gamma}$-$\ensuremath{\gamma}$ coincidence analysis of their decay $\ensuremath{\gamma}$ rays, their ${J}^{\ensuremath{\pi}}$ values were inferred from a comparison to the known decay schemes of the corresponding mirror states in $^{30}\mathrm{Si}$. For the two aforementioned states, our results strongly corroborate the spin-parity assignments assumed in recent evaluations of the $^{29}\mathrm{P}$($p,\ensuremath{\gamma}$)$^{30}\mathrm{S}$ reaction rate.