Beta Decay ofBk250andBk249

Abstract

The beta decay of Bk 250 has been studied with a beta spectrometer. Bk 250 has two beta groups: 725±15 kev (89±1% abundant) and 1760±50 kev (11 ±1% abundant). Conversion electron lines corresponding to 42.2, 98.2, 890, 930, 990, and 1032-kev transitions were observed and their intensities measured. The information obtained from crystal spectrometer singles and coincidence measurements was combined with beta spectrometer data to construct a decay scheme for Bk 250 involving gamma vibrational levels in Cf 250 analogous to those found in Pu 238 . The beta half-life of Bk 250 is 193.3 ±0.3 minutes. The electron capture partial half-life of Bk 250 is estimated to be greater than 50 hours. The beta spectrum of Bk 249 shows an allowed or first-forbidden transition with an end-point energy of 125=b2 kev.

Precise measurements of theBk97249ground state half-life and theβ−-decay end-point energy

“…4, gave an end point energy of 123.6±0.4 keV. This value is in good agreement with that of 123±3 keV measured by Glazov et al [7] and 125±2 keV measured by Vandenbosch et al [6], but our uncertainty is much smaller. It is worth pointing out that AME2012 [18] recommends 124.6±1.4 keV, an average of values in Refs.…”

“…The β − -decay end-point energy of 249 Bk was measured in the past by several investigators [3][4][5][6][7], as indicated in Table I. In the recent Atomic Mass Evaluation (AME2012) [18] a value of 124.6±1.4 keV is recommended.…”

“…In the recent Atomic Mass Evaluation (AME2012) [18] a value of 124.6±1.4 keV is recommended. It is based on the most-precisely known experimental results of 125±2 keV, measured by Vandenbosh et al [6] using a magnetic spectrometer, and 123±3 keV, reported by Glazov et al [7] using a scintillation detector.…”

“…It is worth pointing out that AME2012 [18] recommends 124.6±1.4 keV, an average of values in Refs. [6,7]. Given the recently measured mass of 249 Cf, ME( 249 Cf)=69718.1±1.3 keV [24] and the presently determined value of …”