Spin-isospin flip giant resonances and shell dependence in Li-7 and Be-9 by pi(+) photoproduction

The giant resonances of spin-isospin flip mode are studied by measuring the energy and angular distributions of pi(+) electroproduced from Li-7 and Be -9 nuclei. Several strong pi(+) groups are found and angular distributions of these groups an analyzed by distorted-wave impulse approximation calcula tions using the single particle shell model. The experimental cross section of the groups corresponds to an order of the charge exchange single partic le transition strength, establishing them as spin-isospin flip giant resona nces. The shell model nature of (gamma,pi(+)) results for 1p(3/2) shell nuc lei an summarized and presented together with previously published data. Th e obtained results are compared to previously published data for (pi(-),gam ma), (n,p), (e,e' p), and (p,2p) reactions. Strong transitions consistent w ith the giant resonance excitations from the 1s(1/2) shell in the con and f rom the 1p(3/2) valence shell are observed. [S0556-2813(99)03106-4].