High precision ${}^{89}$Y($\alpha$,$\alpha$)${}^{89}$Y scattering at low energies

Abstract

Elastic scattering cross sections of the ${}^{89}$Y($\alpha$,$\alpha$)${}^{89}$Y reaction have been measured at energies E${}_{c.m.}$ = 15.51 and 18.63 MeV. The high precision data for the semi-magic $N=50$ nucleus ${}^{89}$Y are used to derive a local potential and to evaluate the predictions of global and regional $\alpha$-nucleus potentials. The variation of the elastic alpha scattering cross sections along the $N=50$ isotonic chain is investigated by a study of the ratios of angular distributions for ${}^{89}$Y($\alpha$,$\alpha$)${}^{89}$Y and ${}^{92}$Mo($\alpha$,$\alpha$)${}^{92}$Mo at E${}_{c.m.}\approx$ 15.51 and 18.63 MeV. This ratio is a very sensitive probe at energies close to the Coulomb barrier, where scattering data alone is usually not enough to characterize the different potentials. Furthermore, $\alpha$-cluster states in ${}^{93}$Nb = ${}^{89}$Y $\otimes$ $\alpha$ are investigated.