New evaluation of alpha decay half-life of 190Pt isotope for the Pt–Os dating system

A semiempirical model based on the quantum mechanical tunnelling mechanism of alpha emission from nuclei has been used to evaluate the half-life of the Pt isotopes. For the important naturally occurring 190Pt isotope, the radiogenic parent in the 190Pt → 186Os dating system, the model yielded a half-life-value of (3.7 ± 0.3) × 1011 y. This is comparable to (3.2 ± 0.1) × 1011 y which was obtained in the last direct counting experiment to measure the alpha activity of 190Pt [O.A.P. Tavares, M.L. Terranova, Radiat. Meas. 27 (1997) 19]. A literature survey of available alpha decay half-life values for 190Pt isotope is also reported. The significant discrepancies found between data obtained by direct counting, indirect geological methods and different calculation models are analysed and discussed.