Scattering of polarized7Lifrom4He

Abstract

Complete sets of analyzing powers for elastic and inelastic (to the ${1/2}^{\ensuremath{-}}$ first excited and ${7/2}^{\ensuremath{-}}$ resonant states of ${}^{7}\mathrm{Li})$ scattering of polarized ${}^{7}\mathrm{Li}$ by ${}^{4}\mathrm{He}$ have been obtained. Relations between the different analyzing powers were determined by applying the invariant amplitude method. A comparison of these relations with the measured analyzing powers suggests that the odd rank tensor analyzing powers arise from higher order quadrupole interactions. The quadrupole interaction also gives rise to the inelastic analyzing powers. Continuum-discretized coupled-channels calculations using $\ensuremath{\alpha}+t$ cluster-folded potentials confirm this crucial role of the quadrupole interaction in producing the observed ${}^{7}\mathrm{Li}{+}^{4}\mathrm{He}$ analyzing powers. Cluster-folded spin-orbit and third rank tensor potentials were found to have negligible effects, in contrast to polarized deuteron elastic scattering where the spin-orbit potential plays the dominant role, even in producing the second rank analyzing powers. Coupling between the excited states of ${}^{7}\mathrm{Li},$ in particular that between the 0.478 MeV ${1/2}^{\ensuremath{-}}$ and the 6.68 MeV ${5/2}^{\ensuremath{-}}$ states, was also found to be important.