Electron capture decay of 245Bk (4.90 d) and 246Bk (1.80 d)

Abstract

The electron capture decay schemes of 245Bk and 246Bk have been investigated by measuring the γ-ray and conversion-electron spectra of mass-separated 245Bk and 246Bk samples. The γ-ray spectra were measured with a 25 cm 3 Ge(Li) spectrometer and the conversion-electron spectra were measured with a cooled Si (Li) detector. Multipolarities of most of the transitions in 245Cm and 246Cm were deduced. The half-lives of 245Bk and 246Bk were determined by following the decay of the 252.85 and 798.7 keV photopeaks and were found to be 4.90 ± 0.03 d and 1.80 ± 0.02 d, respectively. The α/(α+EC) ratio for the 245Bk decay was measured to be (1.2 ± 0.1) × 10 −3. On the basis of the present investigation the following non-rotational states were identified in 245Cm: 7 2 + [624], 0; 5 2 + [622], 252.85; 1 2 + 355.95; 3 2 − vibrational, 633.65; and 1 2 + [620], 740.95 keV. The 3 2 − state at 633.65 keV is int as a K π = 2 − phonon coupled to the i 7 2 + [624] single-particle state. Our measurements of 246Bk γ-ray and conversion-electron energies and intensities confirm previous level assignments in 246Cm.