https://doi.org/10.1140/epja/i2011-11155-7
Regular Article - Experimental Physics
Beta and gamma decays of J π = 1+, 24mAl state
β and γ branching ratios
1
Department of Physics, Osaka University, 560-0043, Toyonaka, Osaka, Japan
2
Physics Department, Istanbul University, 34134, Istanbul, Turkey
3
RIKEN Nishina Center, 351-0198, Wako, Saitama, Japan
4
National Institute of Radiological Sciences, 263-8555, Inage-ku, Chiba, Japan
5
Kochi University of Technology, 782-8502, Kami, Kochi, Japan
6
Instituto de Física Corpuscular, CSIC-University of Valencia, E-46071, Valencia, Spain
* e-mail: dnishimu@ribf.riken.jp
Received:
18
August
2011
Revised:
26
October
2011
Accepted:
17
November
2011
Published online:
21
December
2011
A β-γ spectroscopy of the J π , 426 keV isomeric state of 24Al (24m Al) has been carried out by using a 24Al secondary beam with high purity and high isomeric ratio. From the absolute γ-ray and β-particle intensities observed in the decay of the isomeric state, the branching ratio R B of the isomeric γ decay from 24m Al to the J π = 4+, ground state of 24Al have been derived. The obtained R B value of 69.6(7)% is much smaller than the previously accepted value of 82.5(30)%. The precise half-life for the isomer decay, T 1/2 m = 130.9(13) ms, has been also determined in this experiment. Accordingly, the M3 γ-decay strength B(M3) of the 24m Al decay becomes smaller and the total β-decay branching ratio becomes larger. In particular, the β-decay branching ratio to the ground state of 24Mg becomes 24.3(9)%, which is 2.4 times larger than the previous value of 10.1(28)%. By combining the branching ratio and the half-life, the Gamow-Teller (GT) transition strength B(GT) of 0.0194(7) is deduced for the GT transition from 24m Al to the J π = 0+, ground state of 24Mg. This value is in good agreement with the values derived from charge-exchange reactions.
© SIF, Springer-Verlag Berlin Heidelberg, 2011
