Partial alpha-decay half-lives for alpha-emitting Osmium isotopes: Accurate determinations by a semi-empirical model

Abstract Partial alpha-decay half-life-values for twenty-four cases of alpha-decaying Osmium isotopes (161−174, 184, 186−188Os) have been obtained in the framework of a semi-empirical, one-parameter model based on the quantum mechanical tunneling mechanism through a potential barrier. Here the Coulomb, centrifugal and overlapping contributions to the barrier have been considered within the spherical nucleus approximation. The calculation method enabled to reproduce, within a factor 2, the measured half-lives for ground-state to ground-state (gs-gs) α-transitions of twelve artificially produced Osmium isotopes (162−172, 174Os) and of two naturally occurring isotopes (184, 186Os). In addition, a half-life prediction of T½ = (2.0 ± 0.1) × 1016 a has been found for the gs-gs α-transition of naturally occurring 187Os isotope. Two cases of gamma quanta accompanying α-decay possible of being accessed experimentally have been predicted: 184Os decaying to the first level of 180W, with T½ = (0.73 ± 0.04) × 1015 a, and 186Os decaying to the first level of 182W, with T½ = (3.9 ± 0.2) × 1016 a. New α-decay schemes for 184Os, 186Os, 187Os isotopes have been anticipated, and estimated T½-values for rarer cases of α-transitions of Osmium isotopes have been reported.