Structure of the doubly odd nucleus 180Ta : Description of 23 bands

Abstract

The structure of the doubly-odd nucleus 180Ta has been studied by γ– γ coincidence measurements with a DC beam at 52 and 57 MeV and time-correlated γ– γ coincidence measurements with a pulsed beam at 55 MeV via the 176Yb( 11B, α3n) 180Ta reaction. In all measurements, γ-rays were detected in coincidence with charged particles. In the time-correlated γ– γ coincidence measurements with a pulsed 11B beam, three rotational bands and one octupole vibrational band have been identified above the I π =15 − T 1/2=30 μs isomer. The configuration of three bands built on 8 + states has been discussed by means of three-band mixing calculations. BCS calculations with blocking have been used in support of configuration assignment of four- and six-quasiparticle structures. Totally, 19 rotational bands, one β-, one γ- and two octupole-vibrational bands, plus one intrinsic state have been identified with two-, four- and six-quasiparticle configurations. The K values of these bands range from 0 to 19. The K-forbidden transition rates are discussed on the basis of mixing between states with widely different K-values. The BBCS calculations predict a K π =22 − isomer not identified experimentally in this nor in previous works. A search for specific intermediate states which could explain the transformation from K π =9 − to 1 + during the astrophysical s- and r- processes was negative.