Shell-model calculation of transition probabilities between A = 31 even-parity states

Abstract

Shell-model wave functions, incorporating particles in the 2s1/2 and 1d3/2 sub-shells and up to two holes in the d5/2 sub-shell, have been used to calculate M1 and E2 transition probabilities in 31P, the log ft values for the 31S and 31Si beta decay, and the 31P magnetic moment μ. Very good agreement with experiment is obtained for the largest M1 strengths, for the log ft values and for μ, if the isovector part of the matrix element is quenched, and for the E2 strengths (standard deviation 20%) if the average effective charge 1/2(ep+en) is allowed to increase linearly with average excitation energy. All E2 transitions are highly fragmented, whereas the strong M1 transitions derive their strength from just one or two components.