Shape factor analysis of beta transitions in Pm-149

Abstract

Shape factor analysis of the beta transitions in 149pm is carried out for the first time, employing an intermediate image beta ray spectrometer. The ambigous situation arising from the disagreement between reported values in end point energies and intensities of the beta transitions is clarified. An attempt was made to evaluate the NME, for the 780 keV beta transition, using Simms formalism.

First forbidden beta decay in149Pm

“…The ground state beta decay of 149pm with an end-point energy of 786keV populating the 286keV level is of present interest. Its beta spectrum shape was reported to be of statistical nature [2]. The ~-value (=~Z/2R where ~ is the fine structure constant, Z is the charge of the daughter nucleus and R is the nuclear radius) is 13.8 which is much larger than W o-1 (=1.541) where W o is the end-point energy in mc 2 units.…”