Investigation of excited states inMg22via resonant elastic scattering ofNa21+pand its astrophysical implications

Abstract

The excited states in $^{22}\mathrm{Mg}$ have been investigated by the resonant elastic scattering of $^{21}\mathrm{Na}$$+p$. A 4.0 MeV/nucleon $^{21}\mathrm{Na}$ beam was separated by the Center for Nuclear Study (CNS) radioactive ion beam separator (CRIB) and then used to bombard a thick (CH${}_{2}$)${}_{n}$ target. The energy spectra of recoiled protons were measured at scattering angles of ${\ensuremath{\theta}}_{\mathrm{c}.\mathrm{m}.}\ensuremath{\approx}172{}^{\ensuremath{\circ}},146{}^{\ensuremath{\circ}}$, and ${134}^{\ensuremath{\circ}}$, respectively. A wide energy-range of excitation function in $^{22}\mathrm{Mg}$ (up to ${E}_{x}~8.9$ MeV) was obtained simultaneously with a thick-target method, and a state at 7.06 MeV was newly observed. The resonant parameters were deduced from an $R$-matrix analysis of the center-of-mass (c.m.) differential cross-section data with a SAMMY-M6-BETA code. The astrophysical resonant reaction rate for the $^{18}\mathrm{Ne}$($\ensuremath{\alpha},p$)$^{21}\mathrm{Na}$ reaction was recalculated based on the present parameters. Generally speaking, the present rates are much smaller than the previous ones.