Gamow-Teller strength in the 26Mg(p,n)26Al reaction at 135 MeV and its fractionation into T= 0, 1, and 2 isospin channels.

Abstract

The excitation-energy distribution of transition strength to 1/sup +/ states excited via the /sup 26/Mg(p,n)/sup 26/Al reaction at 134.4 MeV was measured for excitation energies up to 25 MeV. The structures observed in the neutron spectra with ..delta..L = 0 angular distributions were identified as 1/sup +/ states, except for the isobaric analog transition. The total 1/sup +/ strength in this reaction was extracted by normalizing the intensity of the four lowest 1/sup +/ states to the strength measured for the analogous beta decays to these states. A detailed comparison of the experimental results with known analogous transitions and with a large-basis shell-model calculation leads to the conclusion that strengths to states of isospin T = 0, 1, and 2 were observed in this reaction. The apportionment of the observed strength among the three isospin values is compared with the shell-model prediction. The total strength observed to all states below an excitation energy of 15 MeV is 57 percent of the total strength predicted by the shell-model calculation with the assumption of the ''free-nucleon'' normalization of the Gamow-Teller beta decay operator.