Li7(α, n)B10Reaction

The ${\mathrm{Li}}^7(\alpha , n){\mathrm{B}}^{10}$ reaction has been investigated by two independent methods. In the first method the energies of the neutron groups were measured with a proton recoil telescope using an integral range technique. In the second method slow neutrons were observed at the threshold energies for each level with an enriched B${\mathrm{F}}_3$ counter. The combined results of the two methods give energy levels in ${\mathrm{B}}^{10}$ at excitation energies of 0.74, 1.31, and 1.72±0.06 Mev, with a ground-state $Q$-value for the reaction of -2.82±0.10 Mev. A comparative experiment with a ${\mathrm{Li}}^6$ target was carried out so that positive assignment of the levels to ${\mathrm{B}}^{10}$ could be made. This work confirms the existence of a second excited state in ${\mathrm{B}}^{10}$ at 1.3-Mev excitation. The 1.3-Mev level had been observed in an early slow-neutron threshold experiment using the ${\mathrm{Li}}^7(\alpha , n){\mathrm{B}}^{10}$ reaction, but it has not been found in other reactions leading to the same final nucleus.