Suppression of Gamow-Teller and M1 transitions in deformed mirror nuclei Mg-25 and Al-25 - 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

*Corresponding author for this work

    Research output: Contribution to journalArticleAcademicpeer-review

    15 Citations (Scopus)

    Abstract

    The mirror nuclei Mg-25 and Al-25 are expected to have very similar structures. The Gamow-Teller (GT) transitions from the J(pi) = 5/2(+) ground state of Mg-25 to the excited states in Al-25 were studied by high-resolution measurements of the Mg-25(He-3,t) charge-exchange reaction at 0degrees and at 140 MeV/nucleon. Assuming the usual DeltaJ(pi) = 1(+) selection rule for the spin-isospin-type GT transitions, the states with J(pi) = 3/2(+), 5/2(+), and 7/2 (+) should be excited. However, of the more than ten states with these J(pi) values below 6 MeV excitation energy, only the 5/2 (+) ground state and the 7/2 (+) , 1.613 MeV state in Al-25 were strongly populated, while all other states were strongly suppressed. The analysis of M1 transitions in Mg-25 also suggested a very similar feature for the analogous M1 transitions. Both Mg-25 and Al-25 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
    Volume19
    Issue number1
    DOIs
    Publication statusPublished - Jan-2004

    Keywords

    • INTERMEDIATE ENERGIES
    • MATRIX-ELEMENTS
    • GRAND-RAIDEN
    • BEAM LINE
    • SPECTROMETER
    • EXCITATIONS
    • SCATTERING
    • STRENGTH
    • STATES
    • SPIN

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