The analog of the 4.7-MeV state of the ${}_{}{}^9{}_{}{}^{}\mathrm{Be}$ nucleus has been observed in its mirror ${}_{}{}^9{}_{}{}^{}\mathrm{B}$ by the reaction ${}_{}{}^{10}{}_{}{}^{}\mathrm{B}({}_{}{}^3{}_{}{}^{}\mathrm{He},\alpha ){}_{}{}^9{}_{}{}^{}\mathrm{B}\left(\alpha \right){}_{}{}^3{}_{}{}^{}\mathrm{Li}_{(\mathrm{g}.\mathrm{s}.\mathrm{})}^{}{}_{}{}^{}$ at $E\left({}_{}{}^3{}_{}{}^{}\mathrm{He}\right)=2.3\mathrm{} \mathrm{and} 5.0$ MeV. The excitation energy and width of the state have been deduced. The value of 1.5 ± 0.3 MeV found for the width is in line with the value deduced by the reaction ${}_{}{}^7{}_{}{}^{}\mathrm{Li}({}_{}{}^3{}_{}{}^{}\mathrm{He},n){}_{}{}^9{}_{}{}^{}\mathrm{B}$, but it is larger by a factor of about 4 than the one measured by the proton following the ${\beta }^{+}$ decay of the ${}_{}{}^9{}_{}{}^{}\mathrm{C}$ nucleus.

• Received 23 July 1986

DOI:https://doi.org/10.1103/PhysRevLett.57.1839