alpha-decay properties of Po-190 and the identification of Po-191

The cy-decay properties of Po-190 were investigated through the use of a fragment mass analyzer in conjunction with a double-sided Si strip detector. The isotope was produced via the Mo-96(Mo-96,2n) reaction, and its alpha-decay energy and T-1/2 were measured as 7529(10) keV and 2.4(-0.3)(+0.4) ms, respectively. The resulting reduced width is nearly identical to that of the Po-192.194 isotopes. This is believed to result from significant mixing between the ground state pi(2p) and the low-lying O(+)pi(4p-2h) intruder state in the Po parent. The result provides further evidence for shape coexistence in the light Po isotopes. In addition, Po-191 was unambiguously identified, and the Pb-186 alpha-decay branch was determined experimentally for the first time.