LABORATORI NAZIONALI DI LEGNARO
High-spin level structure in 184Au has been investigated using the multidetector array of GASP via the 159Tb(29Si,4n)184Au reaction at a beam energy of 140 MeV. Four previously known bands have been extended up to lower and higher spin states and five bands have been newly identified. The excited pi13/2Äni13/2 2-qp band exhibits an upbend with 5 hbar alignment gains at 0.25 MeV. This is interpreted as resulting from a pair of h9/2 alignment. The low-frequency alignment is supported by the measured B(M1)/B(E2) ratios. Consequently, one may attribute the first band crossing in the pi13/2 band of 183Au and the ground-state band of 182Pt to the simultaneous ph9/2 and ni13/2 alignments at degenerate frequencies. The linking transitions between the pi13/2Äni13/2 band and the ground state band have been established leading to a firm spin-and-parity assignment for the pi13/2Äni13/2 band in 184Au. This result provides a strong evidence for the low-spin signature inversion in the pi13/2Äni13/2 bands of odd-odd nuclei in A=180 mass region. In addition, two bands with strong in-band DI=1 transitions have been found; one of them could be interpreted as the prolate ph11/2Äni13/2 band frequently observed in A=160 region, and the other is similar to the oblate ph11/2Äni13/2 structures in 186-192Au. We have identified an excited band which almost degenerates with the ph9/2Äni13/2 prolate band.

DATA: 03-02-2005

Sito Collegato : http://www.lnl.infn.it/~seminari/2005/03Feb_05.html