The Gamma-Radiation from Boron Bombarded by Protons

Employing a Wilson cloud chamber we have determined the distribution in energy of pairs and recoil electrons ejected from lead and carbon laminae by the gamma-radiation from boron bombarded by protons. Both the pair and electron distributions indicate three prominent gamma-ray components at 4.3±0.3 Mev, 11.8±0.5 Mev, and 16.6±0.6 Mev with relative intensities of 1: 1: $\frac{1}{7}$, respectively. The radiation is believed to result from proton capture by ${\mathrm{B}}^{11}$ to form an excited state of ${\mathrm{C}}^{12}$ which radiates in a single transition to the ground state or in a double transition through the well-known intermediate state at 4.3 Mev. Resonance in the yield has been found only in the region 150→200 kv and the total yield of quanta per incident proton above resonance on a thick boron target is estimated to be ≥5×${10}^{-10\mathrm{}}$.