https://doi.org/10.1140/epja/i2003-10115-2
Suppression of Gamow-Teller and M1 transitions in deformed mirror nuclei 25Mg and 25Al
Direct observation of K selection rules
1
Department of Physics, Osaka University, 560-0043, Osaka, Toyonaka, Japan
2
Research Center for Nuclear Physics, Osaka University, 567-0047, Osaka, Ibaraki, Japan
3
Kernfysisch Versneller Instituut, Zernikelaan 25, 9747, AA Groningen, The Netherlands
4
Division of Mathematical Physics, LTH, University of Lund, P.O. Box 118, S-22100 , Lund, Sweden
5
Department of Physics, Kyoto University, 606-8502, Kyoto, Sakyo, Japan
* e-mail: fujita@rcnp.osaka-u.ac.jp
The mirror nuclei 25Mg and 25Al are expected to have very similar structures. The Gamow-Teller (GT) transitions from the ground state of 25Mg to the excited states in 25Al were studied by high-resolution measurements of the 25Mg(
) charge-exchange reaction at
and at 140 MeV/nucleon. Assuming the usual
selection rule for the spin-isospin-type GT transitions, the states with
, and 7/2 + should be excited. However, of the more than ten states with these
values below 6 MeV excitation energy, only the 5/2 + ground state and the 7/2 + , 1.613 MeV state in 25Al were strongly populated, while all other states were strongly suppressed. The analysis of M1 transitions in 25Mg also suggested a very similar feature for the analogous M1 transitions. Both 25Mg and 25Al are known to be largely deformed, and most low-lying states can be interpreted in terms of one-particle quantum numbers in the deformed potential and the associated rotational spectra. The observed suppression can be explained in terms of the K quantum number selection rules that are inherent to axially deformed nuclei.-1
© Società Italiana di Fisica and Springer-Verlag, 2004