High-spin rotational states in 179Os

The rotational bands of the osmium isotopes display very interesting properties that vary with the neutron number. On the one hand the yrast bands of 182,184,186Os display a sudden and rather strong gain in aligned angular momentum,, whereas the lighter osmium nuclei such as 176,178,180Os show a more gradual increase of alignment characteristic of strongly interacting bands. In addition, an unusual rotational band has been found in 178Os. It consists of seven regularly spaced transitions about 36 keV apart which correspond closely to the spacing of the superdeformed band in 152Dy after an A5/3 normalization. this band populates the yrast band directly, and the moment of inertia J(1) is found to be much smaller than J(2). The most likely interpretation of this is a band with large deformation which is undergoing systematic changes in deformation, pairing and/or alignment. This latter finding in particular motivated us to carry out research on the higher spin states in 179Os. Dracoulis et al. have published their results on 5 rotational bands in 179Os. In the present work we found six new bands and extended appreciably the spin limits in the other five. (author). 5 refs., 3 figs