States inC12Between 16.4 and 19.6 MeV

Abstract

The states of ${\mathrm{C}}^{12}$ in the energy region $16.4 \mathrm{MeV}<E_x\left({\mathrm{C}}^{12*}\right)<\mathrm{}19.6\mathrm{} \mathrm{MeV}$ have been studied by bombarding ${\mathrm{B}}^{11}$ with protons in the range $0.5 \mathrm{MeV}<E_p<4.0\mathrm{} \mathrm{MeV}$. Many angular distributions and yield curves were measured for the capture gamma rays forming the ground state and first excited state of ${\mathrm{C}}^{12}$ and for the alpha-particle transitions to the ground state and first excited state of ${\mathrm{Be}}^8$. The total-neutron-yield curve was determined by measuring the yield of residual ${\mathrm{C}}^{11}$ activity. The absolute inelastic proton-scattering cross section was also determined and used to normalize the relative-yield curve of other investigators. The elastic proton scattering was measured as a function of energy at several angles. Some $\gamma -\gamma$ angular-correlation measurements were made at one resonance. In all, nine distinct resonances were studied and given spin, parity, and isospin assignments with varying degrees of completeness. In most cases in which earlier assignments had been made, these assignments were confirmed. The observed levels are compared with those predicted by particle-hole calculations. It is concluded that the particle-hole model is consistent with most of the observed structure, and that all of the predicted levels in this region have been at least tentatively identified.