Recoil-distance lifetime measurements of levels in 36Ar and 36Cl

Abstract

Lifetimes of levels in 36Ar and 36Cl populated in the 2H( 35Cl, n) and 2H( 35Cl, p) reactions, respectively, were measured with the recoil distance method. Gamma rays were detected in coincidence with a neutron detector to study the 36Ar levels and in singles to study the 36Cl levels. Mean lifetimes τ m = 125 ± 20, 19.6 ± 3.1 and 4.1 ± 0.9 ps were obtained from decay curves for the 36Ar levels at 5171, 4974 and 4178 keV, respectively and τ m = 23 ± 2, 10.4 ± 0.5, 2.95 ± 0.14 and 4.9 ± 1.0 ps for 36Cl levels at 788, 1165, 1951 and 2810 keV, respectively. Shell-model calculations, with a model space comprising selected 5h-1p configurations and with an effective charge of 0.5 e, are compared to the transition rates for the low-lying negative parity states in 36Ar.