The 9.155, 9.83, and 10.69 MeV states in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ are found to have large cross sections in both three- and four-particle transfer reactions from a study of the ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$,$\alpha \gamma$), ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^6{}_{}{}^{}\mathrm{Li}$,${}_{}{}^3{}_{}{}^{}\mathrm{He}\gamma$), and ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$,$t\gamma$) reactions at $E_{\mathrm{Li}}=28, 34,\mathrm{and} 28$ MeV, respectively. These results are in disagreement with simple cluster model arguments. Doppler shift attenuation measurements of the lifetimes of the ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$ states show that neither the weak-coupling shell model nor the cluster model accurately predicts the electromagnetic decay strengths in ${}_{}{}^{15}{}_{}{}^{}\mathrm{N}$.

NUCLEAR STRUCTURE ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, $\alpha \gamma$), ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}$(${}_{}{}^7{}_{}{}^{}\mathrm{Li}$, $t\gamma$), $E=28\mathrm{}$ MeV, ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$(${}_{}{}^6{}_{}{}^{}\mathrm{Li}$, ${}_{}{}^3{}_{}{}^{}\mathrm{He}\gamma$), $E=34\mathrm{}$ MeV; particle-$\gamma$ coincidence; Ge(Li) detectors; measured relative cross sections for all states below 10.8 MeV excitation; measured lifetimes; measured $\gamma$-ray branching ratios; compared results to cluster and shell models.

• Received 3 April 1979

DOI:https://doi.org/10.1103/PhysRevC.20.1383