Decay of Gd 153

Abstract

The decay by electron capture of Gd 153 (half-life 236 days) is studied with a coincidence Scintillation Spectrometer. Two gamma-rays are observed with energies 72±8 keV and 100±4 keV and relative intensities of 7:100. Both these gamma-rays are coincident with K X-rays of Eu. From the coincidence data the K-shell conversion coefficient of the 100 keV gamma transition has been determined to be 0.67±0.12; the comparison with theory then leads to assigning this gamma-ray predominantly to a magnetic dipole transition. From the experimental L/K capture ratio the energy involved in the capture process is estimated. Our results show that the levels in Eu 153 which are reached by the capture decay of Gd 153 are not identical with the levels that were observed in coulomb excitation of Eu. On the basis of our findings we propose a decay scheme for Gd 153.