The first excited state of ${}_{}{}^9{}_{}{}^{}\mathrm{C}$ and its analog in ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ have been observed, and their mass excesses and widths have been measured. This completes a new mass quartet which differs from the predictions of the isobaric multiple mass equation less significantly than the ground state $A=9\mathrm{}$ quartet.

NUCLEAR REACTIONS ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ (${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{He}$), $E=74\mathrm{}$ MeV measured $E_x$ of ${}_{}{}^9{}_{}{}^{}\mathrm{C}$ first excited state. ${}_{}{}^{11}{}_{}{}^{}\mathrm{B}\mathrm{}(p,t)\mathrm{}$, $E=46.5\mathrm{}$ MeV, measured $E_x$ of second $T=\frac{3}{2}$ level in ${}_{}{}^9{}_{}{}^{}\mathrm{B}$. Decuced coefficient of multiplet mass equation for first excited $A=9\mathrm{}$ quartet.

• Received 12 August 1974

DOI:https://doi.org/10.1103/PhysRevC.10.2633