alpha-decay characteristics of neutron-deficient Po-190,Po-192 nuclei and alpha branching ratios of Pb-186,Pb-188 isotopes

By using complete fusion reactions S-32+ Er-164 and Ti-48+ Sm-144, leading to Po-196 and Po-192 compound nuclei, improved alpha-decay characteristics for neutron-deficient Po-190,Po-192 isotopes have been obtained. The experi ments have been performed at the fragment mass analyzer (Argonne) and at th e RITU gas-filled separator (Jyvaskyla). In Po-192 the l = 0 decay to the e xcited 0(+) state in Pb-188 is two times faster than the decay to the groun d state. For Po-190 more precise values of the alpha-decay energy E-alpha = 7545(15) keV and half-life T-1/2 = 2.53(33) ms were measured. By using cor related alpha-decay chains alpha-branching ratios of 38(9)% and 9.3(8)% wer e experimentally deduced for the first time for Pb-186 and Pb-188, respecti vely. The reduced alpha-width systematics is extended for even Po isotopes, confirming a persistence of the saturation towards the lighter isotopes. A bsence of any anomalies in the reduced alpha-widths for the neutron-deficie nt Pb isotopes is confirmed.