Transition properties of low-lying states in ${}^{28}$Si probed via inelastic proton and alpha scattering

Abstract

$0^{+}$, $1^{-}$, $2^{+}$, and $3^{-}$ excitations of ${}^{28}\text{Si}$ are investigated via proton and $\alpha$ inelastic scattering off ${}^{28}\text{Si}$. The structure calculation of ${}^{28}\text{Si}$ is performed with the energy variation after total angular momentum and parity projections in the framework of antisymmetrized molecular dynamics (AMD). As a result of the AMD calculation, the oblate ground and prolate bands, $0^{+}$ and $3^{-}$ excitations, and the $1^{-}$ and $3^{-}$ states of the $K^{\pi }=0^{-}$ band are obtained. Using the matter and transition densities of ${}^{28}\text{Si}$ obtained by AMD, microscopic coupled-channel calculations of proton and $\alpha$ scattering off ${}^{28}\text{Si}$ are performed. The proton-${}^{28}\text{Si}$ potentials in the reaction calculation are microscopically derived by folding the Melbourne $g$-matrix $NN$ interaction with the AMD densities of ${}^{28}\text{Si}$. The $\alpha$-${}^{28}\text{Si}$ potentials are obtained by folding the nucleon-${}^{28}\text{Si}$ potentials with an $\alpha$ density. The calculation reasonably reproduces the observed elastic and inelastic cross sections of proton and $\alpha$ scattering. Transition properties are discussed by combining the reaction analysis of proton and $\alpha$ scattering and structure features such as transition strengths and form factors. The isoscalar monopole and dipole transitions are focused.

Comments: 13 pages, 9 figures