Spectroscopy of the Even Zn Isotopes by Inelastic Alpha Scattering

The ($\alpha ,{\alpha }^{\prime }$) reaction, at $E_{\alpha }=31\mathrm{}$ MeV, on ${\mathrm{Zn}}^{68}$ and ${\mathrm{Zn}}^{70}$ was studied with an over-all energy resolution of 70-120 keV. Angular distributions are presented. New $3^{-}$, $4^{+}$, and $5^{-}$ assignments are made on the basis of distorted-wave Born-approximation (DWBA) calculations. Good angular distributions were obtained for double-excitation $2^{+}$ states at 1.88 MeV in ${\mathrm{Zn}}^{68}$ and at 1.78 MeV in ${\mathrm{Zn}}^{70}$. Fractionation of the octupole strength has been observed. Systematics of excitation energies and strengths are discussed for ${\mathrm{Zn}}^{64}$, ${\mathrm{Zn}}^{66}$, ${\mathrm{Zn}}^{68}$, and ${\mathrm{Zn}}^{70}$.