Alpha decay of Gd150

The alpha particle energy and the half-life of Gd150 have been measured with a double-grid ionization chamber. Backgrounds are minimized by the grid-collector coincidence technique. The alpha particle energy is determined as 2.715±0.018 MeV by referring to that of Sm147 (Eα = 2.23±0.02 MeV) reported by Macfarlane. The half-life is estimated to be (1.4±0.4)×106 y from the observed counting rate and the total number of Gd150 nuclei contained in the specimen. The number is estimated from the observed beta-decay rate of the parent nuclei Eu150, which are produced by a photonuclear reaction Eu151(γ, n)Eu150. The experimental half-life thus obtained agrees within a factor of 4.4 with the theoretical half-life calculated from the observed alpha-particle energy on the basis of a conventional barrier-penetration theory. The results show that Gd150 behaves quite normally in the systematics of rare-earth alpha-decay.