AN IBM DESCRIPTION OF COEXISTENCE IN THE PLATINUM ISOTOPES

The available data on the light platinum isotopes have, until now, lac ked calculations which reproduce them. A configuration-mixing calculat ion is presented which describes these nuclei in terms of a normal (ne ar-spherical) and a deformed configuration, the latter becoming the gr ound configuration near neutron mid-shell. The deformed configuration is modelled as a proton pair excitation across the Z = 82 shell gap wi thin the Interacting Boson Model, and allowed to mix with the normal c onfiguration. The systematics of level energies, electromagnetic trans ition rates and moments, isotope and isomer shifts are studied. The la tter are shown to be sensitive probes of the configuration-mixing stre ngth. (C) 1997 Elsevier Science B.V.