Résumé du preprint Irfu-11-13

Irfu-11-13
Measurements of the $\beta$-decay half-lives and $\gamma$-ray emission probabilities of $^{244gs}Am$ and $^{244m}Am$ isotopes for the $^{243}Am$ capture cross sections determination.
A. Letourneau, I. AlMahamid, E. Barat, Th. Dautremer, F. Marie, P. Mutti
Recently it was required by an IAEA Coordinated Research Project further studies on the decay of actinides and in particular on the b-decay of 244Am. In this paper we report on an experiment to measure the b-decay half-lives of the isomeric and the ground states of 244Am. These data were obtained thanks to the use of ADONIS a high counting rate acquisition system. The obtained values amount to T1/2=28.31.3 minutes for 244mAm and T1/2=10.650.12 hours for 244gsAm that is slightly higher than the evaluated ones. Thanks to the use of coupled a- and g-spectroscopic techniques we also measured the total thermal capture cross section and the capture branching ratio to the isomeric state of 244Am which amount to tot = (81:3  2:5) and BR = 0:953  0:02 respectively. Using these measured partial cross sections we have then calculated new absolute g-emission probabilities for the decay of the ground and the isomeric states. No large discrepancies were observed with previous evaluated data, but we largely reduce the uncertainties on the intensities.