First forbidden beta decay in149Pm

Abstract

The 786keV beta-286keV gamma angular correlation in the ground state decay of 149pm is measured for the first time, using the conventional slow-fast scintillation assembly. Integral correlation results characterize the involved beta transition to be of first-forbidden non-unique type. The present results combined with the other experimental parameters, strongly support a 9/2-spin-parity character to the 286keV level in 149Sm. The energy independence of the reduced correlation coefficient as found in this work shows the validity of i-approximation for the 786 keV beta transition in 149pm and is also consistent with the logft value and spectrum shape reported by earlier authors.