Three-particle cluster structure aboveEx=11 MeVin15N

Abstract

${}^{12}\mathrm{C}{(}^{7}\mathrm{Li},\ensuremath{\alpha})$ angular distributions have been obtained for 16 states in ${}^{15}\mathrm{N}$ at ${E(}^{7}\mathrm{Li})=52.5 \mathrm{MeV}$. Also, ${}^{12}\mathrm{C}{(}^{6}\mathrm{Li}\ensuremath{\rightarrow}{,}^{3}\mathrm{He})$ angular distributions and vector analyzing powers have been measured at ${E(}^{6}\mathrm{Li}\ensuremath{\rightarrow})=50 \mathrm{MeV}$. Finite-range distorted-wave Born-approximation (FRDWBA) triton cluster transfer calculations are able to describe the ${(}^{7}\mathrm{Li},\ensuremath{\alpha})$ data for transfer to states with known ${J}^{\ensuremath{\pi}}$ values. Comparison with known levels in ${}^{19}\mathrm{F}$ suggests that the ${}^{12}\mathrm{C}{(}^{7}\mathrm{Li},\ensuremath{\alpha})$ reaction selectively populates negative parity states. FRDWBA calculations support this idea. Several previously suggested ${J}^{\ensuremath{\pi}}$ levels are confirmed and new ${J}^{\ensuremath{\pi}}$ values are proposed for six other levels. The previously observed ${(}^{6}\mathrm{Li}\ensuremath{\rightarrow}{,}^{3}\mathrm{He}) J$ dependence has been used along with coupled-channel Born-approximation calculations to confirm the ${J}^{\ensuremath{\pi}}$ values for states in ${}^{15}\mathrm{N}$.