Suppression of Gamow-Teller and M1 transitions in deformed mirror nuclei 25Mg and 25Al: Direct observation of K selection rules

Y. Shimbara, Y. Fujita, T. Adachi, G. P.A. Berg, H. Fujita, K. Fujita, I. Hamamoto, K. Hatanaka, J. Kamiya, K. Nakanishi, Y. Sakemi, Y. Shimizu, M. Uchida, T. Wakasa, M. Yosoi

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The mirror nuclei 25Mg and 25Al are expected to have very similar structures. The Gamow-Teller (GT) transitions from the J π = 5/2+ ground state of 25Mg to the excited states in 25Al were studied by high-resolution measurements of the 25Mg(3He, t) charge-exchange reaction at 0 ° and at 140 MeV/nucleon. Assuming the usual ΔJ π = 1+ selection rule for the spin-isospin-type GT transitions, the states with Jπ = 3/2+, 5/2 +, and 7/2+ should be excited. However, of the more than ten states with these Jπ 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 Ml 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.

Original languageEnglish
Pages (from-to)25-31
Number of pages7
JournalEuropean Physical Journal A
Issue number1
Publication statusPublished - Jan 2004

All Science Journal Classification (ASJC) codes

  • Nuclear and High Energy Physics


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