Isospin effects in nuclear vibrations

A review of the evidence that the ratio of neutron and proton multipole matrix elements for collective vibrations in single-closed-shell nuclei differ systematically from N/Z is presented. A theoretical framework is given for understanding the data on the basis of the ideas of core polarization. It follows that nuclear deformation parameters are probe dependent and that analysis of excitations by two different probes such as (p,p') and (n,n') can, in principle, give the ratio M/sub n//M/sub p/. Application is made to first 2+ states of open shell nuclei. Trends of M/sub n//M/sub p/ for higher 2+ states are presented. Expected systematics of M/sub n//M/sub p/ ratios for giant isoscalar quadrupole transitions are presented. 22 references