Nuclear spectroscopy ofOs189

Forty-three states have been observed up to an energy of 1474 keV in ${}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$ using the reactions ${}_{}{}^{188}{}_{}{}^{}\mathrm{Os}\mathrm{}(d,p)\mathrm{}{}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$ and ${}_{}{}^{190}{}_{}{}^{}\mathrm{Os}\mathrm{}(d,t)\mathrm{}{}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$, produced with 12 MeV deuterons, and the ${}_{}{}^{188}{}_{}{}^{}\mathrm{Os}(n,\gamma ){}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$ reaction using thermal neutrons and observing $\gamma$ rays from 36 to 5933 keV. The neutron separation energy of ${}_{}{}^{189}{}_{}{}^{}\mathrm{Os}$ was determined to be 5920.8 ± 2.0 keV in agreement with the value of the ($d,p$) reaction. The $Q$ value for the ${}_{}{}^{190}{}_{}{}^{}\mathrm{Os}\mathrm{}(d,t)\mathrm{}{}_{}{}^{180}{}_{}{}^{}\mathrm{Os}$ reaction was measured to be -1530 ± 4 keV. Using $l$-transfer results, spin-parities were assigned to 14 states. A number of states up to 818 keV were qualiatively interpreted in terms of the Nilsson model. Anomalous Nilsson systematics particularly of the 1/2-[510] and 3/2-[512] bands involving anomalously large ($d,p$) and ($d,t$) cross sections populating the 5/2- and 3/2- states at 69.6 and 95.3 keV, respectively, are interpreted in terms of decreasing deformation and the consequent increase in Coriolis coupling. The low lying 5/2- state at 276 keV is interpreted as the lowest rotational state built on the 9/2-[505] level at 30.8 keV. This implies triaxiality for this configuration.