A STUDY OF T =3/2 STATES IN N-13

A study of T=32 states in N13 was carried out by observing these states as resonances in the compound system C12+p The lowest T=32 state was observed as a resonance in the proton elastic scattering at Ep=14.2310.004 MeV. A search for additional T=32 states was carried out by measuring excitation functions for elastic scattering and for several proton-induced reactions over the proton energy range 17.0-21.5 MeV; two anomalies were found at Ep=17.80 and 18.459 MeV, whose widths and locations suggest that they might correspond to T=32 states. In order to obtain the spins, parities, and elastic partial widths for the observed resonances, a program of phase-shift analysis was carried out using optical-model phases plus a single-level dispersion term. Such an analysis of the 14.231-MeV resonance yielded the assignment of J=32-. From a similar analysis, one obtains J=32+ for the 17.80-MeV resonance, while the 18.459-MeV resonance was limited to spin and parity assignments of 32- or 72+. These assignments for the 17.80- and 18.459-MeV resonances, and the observed intensities for their proton decay to the 15.11-MeV state in C12 are consistent with their identification as T=32 states. Five other resonances, thought to correspond to T=12 states, were observed at Ep=13.035, 15.220, 17.67, 19.40, and 19.46 MeV and were also analyzed in a similar fashion to yield spin and parity assignments of 32+, 72+, 52-, and 32+, respectively. © 1969 The American Physical Society.