Exotic superdeformed structure in A(approx)190 nuclei observed using Eurogam2

摘要

Dipole transitions between superdeformed rotational bands are only very rarely observed due to the competition from the very strong in-band E2 decays. We have carried out two experiments with the EUROGAM2 (gamma)-ray spectrometer, situated at the Vivitron tandem accelerator at CRN Strasbourg, in September and October 1994. In the first experiment we observe M1 dipole transitions between the signature partner yrast superdeformed bands in (sup 193)Tl. This measurement gives a mean value of (g(sub K)-g(sub R)) K/Q(sub o) = 0.135 (+-) 0.010 (mu)(sub N)/eb identifying the bands as belonging to the (642)5/2 single particle orbital. We also observe 5 additional new superdeformed bands in (sup 193)Tl, whose structures are discussed. In the second experiment we observe three transitions, at 911, 865 and 831 keV, which link an excited superdeformed band in (sup 190)Hg to the yrast superdeformed band. The data suggest that these are stretched dipole transitions with E1 multipolarity and strengths of about 10(sup -3)Wu. This is the first observation of a collective vibration of the superdeformed mean field. We also observe two new superdeformed bands in (sup 190)Hg. (authors). 39 refs., 11 figs., 3 tabs. (Atomindex citation 27:071581)