Osmium isotopes with the (p,t) reaction

The (p, t) reaction at E/subp/=19.0 MeV has been used to study five isotopes of Os (A=190, 188, 184, 187, 185) which lie in a transition region between the deformed rare earths and spherical nuclei. Cross sections and angular distributions have been measured to states up to about 2 MeV of excitation in all cases except /sup 188/Os and /sup 190/Os in which states were seen up to 4 MeV. The energies of the J/sup pi/=0/sup +/ states which we see and their summed cross sections in percent of the ground state (in parenthesis) are: 913 (4.7), 1551 (1.8), and 1734 keV (6.3) in /sup 190/Os, 1087 (5.7), 1480 (3.7), 1705 (1.2), and 1765 keV (<1) in /sup 188/Os, and 1042 (8.4) and tentatively 1982 (1.2) and 2268 keV (1.3) in /sup 184/Os. The L=0 transitions seen in the odd isotopes are at 9.8, 77, 730, and 1657 keV in /sup 187/Os and 1070 and 1213 keV in /sup 185/Os. The results show no positive evidence for the existence of strongly populated shape isomeric 0/sup +/ states similar to those seen in the transition region around N=88. In /sup 188/,/sup 190/Os and possibly /sup 192/Os the lowest exicted K=0 andmore » K=4 bands have the properties expected for two-phonon ..gamma..-vibrations. In addition to the rotational excitations in the odd isotopes, two strong transitions have been seen to states at 599 and 802 keV in /sup 185/Os which we have postulated to be the vertical-barK/sub 0/ +- 2vertical-bar ..gamma.. vibrations based on the 1/2/sup -/510 state with admixed one quasiparticle components. Similar states have been seen in /sup 187/Os. The lowest L=0 transfers to states in /sup 185/,/sup 187/Os were found to have significantly lower intensity than the ground states in the adjacent even-N nuclei. In the case of /sup 187/Os the low lying L=0 strength is split between two states. Calculations have been made to understand these phenomena in terms of blocking effects and Coriolis mixing. (AIP)« less