Isospin violation in the 12C(6Li,α)14N (2.31 MeV) reaction

The isospin violating reaction 12C(6Li,α)14N (2.31 MeV) has been investigated in the range of lithium beam energies from 9.0 to 14.0 MeV. Excitation functions were measured for the ground state, 2.31-MeV state and 3.95-MeV state of 14N at 150, 200, 600 and 1600 in the lab. An excitation function at 400 lab was taken for the ground state and 3.95-MeV state of 14N. Angular distributions were obtained at 10.5, 11.25, 13.75 and 20.0-MeV beam energies. The data were taken using a 50 cm. broad-range magnetic spectrograph with a position-sensitive proportional counter in the focal plane, and with solid state detectors in the Ortec scattering chamber. Special isotopically pure carbon targets were used to eliminate the 13C contaminant. The results indicate a 1.2 to 4.5 percent yield to the 2.31-MeV isospin forbidden state as compared to the allowed ground state and 3.95-MeV state in the energy region of 9 to 14 MeV lithium beam energy. At 20.0 MeV the yield to the forbidden state is only 0.1 percent the allowed yield. Isospin mixing by the Coulomb force is believed responsible for the forbidden yield seen between 9-14 MeV. No observation was made of a direct-reaction isospin violating mechanism. The results for 12C(6Li,α)14N for the first three states in 14N with beam energies of 9-14 MeV are compared with the available data from 16O(d,α)14N and 14N(α,α')14N in the same region of the compound nucleus