Using the reaction ${\mathrm{Si}}^{28}(n, \alpha ){\mathrm{Mg}}^{25}$ in a surface-barrier detector as a neutron spectrometer, a comparison measurement is made of the energies of neutron groups from the reaction ${\mathrm{B}}^{10}({\mathrm{He}}^3, n){\mathrm{N}}^{12}$ with ${\mathrm{B}}^{10}(\alpha , n){\mathrm{N}}^{13}$ as a calibration standard. A ground-state $Q$ value, $Q_0=1.561\mathrm{}\pm 0.009$ MeV, is found for ${\mathrm{B}}^{10}({\mathrm{He}}^3, n){\mathrm{N}}^{12}$, and two states of ${\mathrm{N}}^{12}$ are located at excitation energies 0.994±0.020 and 1.22±0.03 MeV.

• Received 7 November 1963

DOI:https://doi.org/10.1103/PhysRev.133.B1504