High-spin state spectroscopy of 88,90Zr.

Abstract

The high-spin states of $^{88}\mathrm{Zr}$ and $^{90}\mathrm{Zr}$ were studied up to \ensuremath{\sim}12-MeV excitation via the $^{74}$,76Ge${(}^{18}$O,4n\ensuremath{\gamma})${}^{8}$ 8,90Zr fusion evaporation reactions. Decay schemes were constructed on the basis of gamma-ray excitation functions, angular distribution and linear polarization measurements, \ensuremath{\gamma}-\ensuremath{\gamma} coincidences, and level lifetimes determined from both Doppler shift attenuation and recoil distance measurements. An effort was made to make as definite spin-parity assignments as possible and to delineate the reliability of these assignments. Probable spins up to \ensuremath{\sim}20\ensuremath{\Elzxh} were formed in both nuclei. The experimental results are compared to preliminary results of a large-scale shell model calculation. The yrast spectra of both nuclei can be interpreted as arising from intrinsic modes of excitation with no evidence for collective behavior.