Level structure in the transitional nucleus 199Tl.

High-spin level structures of 199Tl have been studied by in-beam γ-ray spectroscopic methods using the 196Pt(7Li, 4n)199Tl reaction at 40 MeV of beam energy. A large number of new states have been found, resulting in a significant extension of the previously known level scheme with the observation of 44 new transitions and 33 new levels. By comparing with the level structures in the odd-mass Tl isotopes and the even-even core Hg nuclei, configurations are proposed for the newly observed rotational bands and states in 199Tl. The properties of the strongly coupled positive- and negative-parity bands can be interpreted in terms of the cranked Nilsson-Strutinsky-Bogoliubov model calculations, which show that the observed bands are built on the oblate shapes. [ABSTRACT FROM AUTHOR]