Systematics of alpha-radioactivity in the rare earth region

Abstract

Alpha decay energy data in the rare earth region are extended by means of closed decay energy cycle calculations and are then correlated for each element as a function of neutron number. The marked effect of the closed shell at 82 neutrons on the alpha decay energies is discussed. Evidence is presented for a sharp drop at 90 neutrons in the normal alpha-decay energy versus neutron number trend, as well as for a proton subshell at 64 protons. Half-lives are calculated using a formula derived from simple barrier-penetration theory. The calculated values are compared with experimental half-lives and discrepancies are discussed. Reduced level widths δ 2 are determined for rare earth alpha emitters using barrier penetration factors calculated from the real potential derived by optical model analysis of alpha elastic scattering data. The reduced widths are in turn used to propose hindrance factors for odd-mass alpha emitters.