Gamow-Teller matrix elements from the 12C(d,2He) and 24Mg(d,2He) reactions at 170 MeV

The 24Mg(d,2He)24Na and the 12C(d,2He)12B charge-exchange reactions have been studied at an incident energy of 170 MeV. The two protons in the 1S0(pp) state (indicated as 2He) were both momentum analyzed and detected by the same spectrometer and detector. Background-free 2He spectra with a resolution of about 150 keV (full width at half maximum) have been obtained allowing identification of many levels in the residual nucleus with high precision. It is found that the (d,2He) reaction at 0 deg. is largely governed by the Gamow-Teller (GT) transition operator for the β+ direction, which makes the reaction selective for isovector 1+ transitions. In the case of 24Mg, the reaction is compared with (p,n) reaction data in which the same levels in the analog nucleus 24Al are populated. Angular distributions of cross sections for the (d,2He) reaction are presented and compared with distorted-wave Born approximation calculations. GT matrix elements are deduced. A level-by-level comparison with shell-model calculations using the universal s-d interaction has been performed. Comparison with (p,p') data yields a level scheme for the A=24 isospin triplet