Spin-dipole strength functions of ${}^4$He with realistic nuclear forces

Abstract

Both isoscalar and isovector spin-dipole excitations of ${}^4$He are studied using realistic nuclear forces in the complex scaling method. The ground state of ${}^4$He and discretized continuum states with $J^{\ddot{I}}€=0^{-},1^{-},2^{-}$ for A=4 nuclei are described in explicitly correlated Gaussians reinforced with global vectors for angular motion. Two- and three-body decay channels are specifically treated to take into account final state interactions. The observed resonance energies and widths of the negative-parity levels are all in fair agreement with those calculated from both the spin-dipole and electric-dipole strength functions as well as the energy eigenvalues of the complex scaled Hamiltonian. Spin-dipole sum rules, both non energy-weighted and energy-weighted, are discussed in relation to tensor correlations in the ground state of ${}^4$He.

18 pages, 8 figures