Directional correlation in the β-decay of 211Pb

Abstract

The 970 keV β-transition in the decay of 211Pb to the 7 2 − first excited state of 211Bi has been investigated by measuring the directional correlation of this β-group with the 405 keV cascade γ-ray using a scintillation β-γ coincidence spectrometer. The directional correlation coefficient A 2 is found to be about −30.03 for β-ray energies above 550 keV. This and other available information indicate the most likely J π assignment for 211Pb to be 9 2 + . Assuming this assignment, the directional correlation data were analyzed for β-decay matrix elements using the formulation of Morita and Morita. It is found that the data are very well explained by the Kotani parameters x = 0.75±0.15, y = 33±7 and z = 1.30±0.40. These results are in agreement with expectations based on the CVC theory and shell-model calculations of Rao and Gerace. The ft value for the β-transition is also well reproduced by these matrix elements.