Study of 191Os by average resonance neutron capture: Fragmentation of Nilsson model strength

The ¹⁹⁰Os(n, γ)¹⁹¹Os reaction was studied with the average resonance neutron capture technique at a neutron energy centered on 2 keV. Thermal capture data were also recorded. Primary transitions to states up to an excitation energy of ≈ 1700 keV were detected. From the average capture data it appears possible to distinguish E1 from M1 multipolarities and thereby to map out the $\text{1}\text{2}{}^{\mathrm{?}}\text{,}\text{3}\text{2}{}^{\mathrm{?}}$ states in ¹⁹¹Os. By elimination, it is possible to treat the $\text{J}{}_{\mathrm{\pi }}\text{≠}\text{1}\text{2}{}^{\mathrm{?}}$$\text{3}\text{2}{}^{\mathrm{?}}$ states as well, albeit with greater uncertainty. Combination of these results with existing data from the (d, p) reaction allows an extension of earlier treatments of the fragmentation of Nilsson strength in this mass region. Although other mechanisms may also suffice it is possible to qualitatively interpret the complex fragmentation systematics in terms of a simple model of large hexadecapole deformations varying in a reasonable manner.