Under the assumption that isospin T is a good quantum number, isobaric analog states and various analogous transitions among these states are expected in isobars with mass number A. Strengths of analogous Gamow-Teller (GT) and M1 transitions have been compared for an A = 26 isobar triplet with Tz= +1, 0, and -1, where Tz is defined by Tz = (N-Z)/2. The Tz= + 1 → 0 GT transitions from the Jπ = 0 +ground state of 26Mg to excited Jπ= 1 + states in 26Al were studied up to the excitation energy (Ex) of 9 MeV by using a high energy-resolution (3He,t) reaction. The distribution of observed GT strengths was well reproduced in a shell-model calculation. The isospin symmetric Tz= - 1 → 0 GT transitions can be studied in the 26Si β decay. The GT strengths from the (3He,t) reaction were in good agreement with the β-decay values evaluated up to Ex = 2.7-MeV states in 26Al. The GT strengths were further compared with the strengths of analogous M1 γ transitions in 26Al, i.e., the M1 transitions from the excited 1+ states to the isobaric analog state of the 26Mg ground state in 26Al. Through this comparison, contributions of spin and orbital terms in these Ml transitions were studied. The GT and M1 strengths as well as spin and orbital contributions in M1 strengths are interpreted by both the shell model and the particle-rotor model assuming a correlated proton and neutron pair around a 26Mg core. The isospin T of each excited 1+ state in 26Al was also studied by examining the existence or the nonexistence of the analog 1 + state in the Tz = 1 26Mg nucleus.
|Number of pages||5788092|
|Journal||Physical Review C - Nuclear Physics|
|Publication status||Published - 2003 Jun|
ASJC Scopus subject areas
- Nuclear and High Energy Physics