DISTRIBUTION OF SPIN-ISOSPIN STRENGTHS IN B-12 AND B-13

The differential cross sections of the reactions C-12,C-13(gamma, pi())B-12,B-13 were measured using tagged photons at the mean energy E(ga mma) = 191 MeV at five angles 35 degrees less than or equal to theta(p i) less than or equal to 145 degrees corresponding to the momentum tra nsfer to the nucleus 0.5 less than or equal to q less than or equal to 1.5 fm(-1). The major transition strengths leading to various excited states in B-12,B-13, in, both cases, are concentrated within a resona nce centered at about 7 MeV excitation energy in B-12,B-13 (about 22 M eV in C-12,C-13) with a full width at half maximum (FWHM) of about 12 MeV, reminiscent of the well-known electric-dipole gian resonances. Th e two reactions are compared in the context of the weak-coupling model .