The mass and width of the ${}_{}{}^7{}_{}{}^{}\mathrm{B}$ ground state have been measured using the reaction ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}$(${}_{}{}^3{}_{}{}^{}\mathrm{He}$, ${}_{}{}^6{}_{}{}^{}\mathrm{He}$)${}_{}{}^7{}_{}{}^{}\mathrm{B}$, thus completing the mass-seven isospin quartet. During the course of the experiment new values for the excitation energies of the ${}_{}{}^8{}_{}{}^{}\mathrm{B}$ second excited state and the ${}_{}{}^7{}_{}{}^{}\mathrm{Li}$ and ${}_{}{}^7{}_{}{}^{}\mathrm{Be}$ lowest $T=\frac{3}{2}$ states were found.

• Received 10 November 1967

DOI:https://doi.org/10.1103/PhysRevLett.19.1442