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

Partial alpha-decay half-life-values for twenty-four cases of alpha-decaying Osmium isotopes (^{161-174, 184, 186-188}Os) 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, 174}Os) and of two naturally occurring isotopes (^{184, 186}Os). In addition, a half-life prediction of T_½ = (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 T_½ = (0.73 ± 0.04) × 10¹⁵ a, and ¹⁸⁶Os decaying to the first level of ¹⁸²W, with T_½ = (3.9 ± 0.2) × 10¹⁶ a. New α-decay schemes for ¹⁸⁴Os, ¹⁸⁶Os, ¹⁸⁷Os isotopes have been anticipated, and estimated T_½-values for rarer cases of α-transitions of Osmium isotopes have been reported.