DIPOLE AND SPIN-DIPOLE RESONANCES IN CHARGE-EXCHANGE REACTIONS ON C-12

The C-12(n,p)B-12 reaction was studied using the white neutron source at the Los Alamos Meson Physics Facility/Weapons Neutron Research cent er with a continuous incident neutron energy from 60 to 260 MeV. Doubl e differential cross sections were measured in the angular range 11-de grees less-than-or-equal-to theta(lab) less-than-or-equal-to 37-degree s. Using the neutron time-of-flight facility at the Indiana University Cyclotron Facility, we also studied the C-12(p,n)N-12 reaction at E(p )= 186 MeV and the C-12(p over arrow pointing right, n over arrow poin ting right)N-12 reaction at E(p over arrow pointing right) = 160 and 1 86 MeV. Double differential cross sections were measured between theta (lab) = 0-degrees and theta(lab) = 50-degrees in 5-degrees steps. Spin observables D(NN), A(Y), and P were measured at theta(lab) = 5-degree s, 9-degrees, 13-degrees with E(p over arrow pointing right) = 160 MeV and theta(lab) = 15-degrees, 20-degrees with E(p over arrow pointing right) = 186 MeV. Angular distributions of differential cross section and spin observables for low-lying transitions in the residual nuclei are compared with distorted-wave impulse approximation (DWIA) calculat ions. A multipole decomposition analysis was performed to study the gi ant dipole and giant spin-dipole resonances. The contributions of the quasifree reaction in the giant resonance region were subtracted. The empirical results of energy distributions for dipole (DELTAL = 1) tran sition are compared with DWIA calculations using nuclear structure inf ormation obtained with a conventional shell model and also with a rand om phase approximation.