The proton beams from a pressurized Van de Graaff accelerator were used to irradiate targets of separated ${\mathrm{B}}^{10}$ isotopes, and the $\gamma$-ray spectra and yield curves from the ${\mathrm{B}}^{10}(p, \alpha \gamma ){\mathrm{Be}}^7$, ${\mathrm{B}}^{10}(p, \gamma ){\mathrm{C}}^{11}$ and ${\mathrm{B}}^{10}(p, p^{\prime }\gamma ){\mathrm{B}}^{10}$ reactions were measured by using a large crystal spectrometer and pulse-height analyzer.

The 0.43±0.015 Mev $\gamma$ ray from the ${\mathrm{B}}^{10}(p, \alpha \gamma ){\mathrm{Be}}^7$ reaction was found to have a resonance at 1.540±0.005 Mev, the cross section at resonance being 80±40 millibarns.

The 9.70±0.15 Mev radiation from the ${\mathrm{B}}^{10}(p, \gamma ){\mathrm{C}}^{11}$ reaction exhibited a single resonance at 1.146±0.005 Mev, the cross section at resonance being measured as 5.5±2 μb. $\gamma$ rays of about one-twentieth of this intensity of energy about 4.2 Mev and 5.5 Mev can also be attributed to this resonance.

The yield of 0.71±0.015 Mev radiation from the ${\mathrm{B}}^{10}(p, p^{\prime }\gamma ){\mathrm{B}}^{10}$ increased monotonically with energy. The cross section at 2.7 Mev was 11±5 millibarns. For proton energies of greater than 2.4 Mev, weaker $\gamma$ rays of energy 1.00±0.04 Mev and 2.12±0.06 Mev were also present.

• Received 5 December 1956

DOI:https://doi.org/10.1103/PhysRev.106.1012