| Popis: |
Giant isovector analog E1 resonances have been observed by means of the pion single-charge-exchange reactions ( π ± , π 0 ). The giant T = 1 analog E1 resonances in 12 B and 12 N, built on the ground state of 12 C, were observed in the 12 C( π ± , π 0 ) reactions. The giant T = 3 2 resonances in 13 B and 9 Li, built on the ground states of 13 C and 9 Be, were studied with the 13 C, 9 Be( π − , π 0 ) reactions, respectively. Analogs of these resonances were found in the 13 C, 9 Be( π + , π 0 ) reactions along with lower lying T = 1 2 resonances. These resonances together with the higher T = 3 2 resonances constitute isospin-splitting in the nuclei, 13 N and 9 B. These isospin assignments were made by comparing results from the ( π ± , π 0 ) reactions and their measured angular distributions. The assignments were confirmed by determining the decay properties of the resonances with coincident ( π 0 p) measurements in the ( π + , π 0 p) reactions. The proton angular distributions measured relative to the momentum transfer direction were consistent with a dipole process. |
