The decay of 90Nb

Abstract

The decay of 14.60±0.05 h 90Nb has been investigated with a double-focussing iron-yoke spectrometer and with a Ge(Li) detector. The end-point energy of the intense (53±6%) positon branch has been determined to be 1500±4 keV, leading to a Q-value of 611±5 keV. Some 17 transitions have been found in the internal conversion spectrum, and among these are six not previously reported at 518, 828, 1575, 1717, 1914 and 2223 keV. The K-conversion coefficients have been determined by combining the internal conversion intensities with the gamma-ray intensities. For many transitions, probable multipolarity assignments have been obtained from these coefficients and also from K/ΣL and L I/(L II+L III) ratios. The M-conversion intensities of the 133 and 141 keV transitions have been found to be in agreement with the recent tabulations of Hager and Seltzer. All transitions observed have been fitted into a tentative decay scheme, which in its lower part is in agreement with shell-model calculations.