Identification of excited states in Os-167 and Os-168: shape coexistence at extreme neutron deficiency

Excited states in the very neutron-deficient isotopes Os-167 and Os-168 hav e been observed using the reaction Sn-112(Ni-58, 2pxn). The JUROSPHERE gamm a -ray spectrometer array was used in conjunction with the RITU gas-filled recoil separator to collect prompt gamma radiation in coincidence with reco ils implanted in a silicon strip detector located at the focal plane of RIT U. Using a selective recoil decay tagging technique it has been possible to unambiguously assign gamma -ray transitions to Os-167 and Os-168 through t he characteristic a radioactivity of these nuclides. The high-spin structur e of the bands is discussed in terms of quasiparticle configurations within the framework of the cranked shell model. The role of shape coexistence in Os-168 is examined with phenomenological three-band mixing calculations. ( C) 2001 Elsevier Science B.V. All rights reserved.