Analysis of electromagnetic transitions in A = 120-145 region in quasiparticle model

The notion of quasiparticle is one of the essentials in nuclear theory. Among the interaction of quasiparticles, the one, at once simple and equivalent for many purposes to the strict multipole-multipole interaction, is the Migdal ansatz. Adopting the point of view that its parameters are related to other nuclear properties the spin-spin parameter therein has been extracted for nineteen nuclei in the mass range A=120-145, namely, the isotopes of Te, Xe, Ba, Co, Nd, Sm, Gd. The basic single particle levels are obtained from two sets of potential parameters in a Saxon-Woods shape, one set from an analysis of single particle energies (RML) and the other set from an analysis of neutron scattering (TM). A one shell to one shell transition is envisaged as being the best consistent with notion of quasiparticle. The results are presented and discussed. On an average, the spin-spin interaction has a value 2.2-2.6. The fluctuations either side can be considerable and are found to be correlated with nuclear density variations. There is not much difference between the two sets of potential parameters, which is a very encouraging aspect. (author)