High-spin states in 179Os

The 154Sm(30Si,5n)179Os reaction has been used to study rotational bands at high spin by means of extensive gamma-ray coincidence measurements. The new α=-1/2 signature partner of the 1/2-[521] band has been found up to spin 31/2- and the previously known α=+1/2 partner extended up to spin 45/2-. The α=-1/2 and α=+1/2 components of the previously known 7/2-[514] and the 9/2+[624] bands were extended up to spins 63/2-, 53/2- and 63/2+,61/2+, respectively. The two components of the newly found band 5/2-[512] have been established up to spins 59/2- and 65/2-. In addition, two other new bands were found, one of them with spins up to 61/2+ decays to the 9/2+[624] band. Configurations have been proposed by comparing the signature splittings and the B(M1)/B(E2) ratios with the theoretical predictions. The latter points to rather strong Coriolis interaction between the 5/2-[512] and 7/2-[514] bands. The first band crossing observed in nine out of the ten bands is most probably due to the alignment of a pair of i13/2 neutrons, on the basis of a comparison of experimental Routhians with the cranking shell model calculations. In the three positive-parity sequences and in the α=+1/2 signature of the 5/2-[512] band, second band crossings are also observed that are suggested to be caused by an alignment of two h9/2 protons