Superdeformation and Prolate--Oblate Competition in Tl Nuclei

Spectroscopic studies of weakly populated proton i(13/2) bands in superdeformed Tl nuclei (around mass 190) and in the normally deformed, very light Tl-183 nucleus are discussed. Among the results presented, the first measurement of a superdeformed quadrupole moment in an odd-Z nucleus, Tl-191, is reported. The experiments were conducted with the Gammasphere array as "stand-alone" device and coupled with the Argonne Fragment Mass Analyzer.