The excitation of curve for ${\mathrm{B}}^{11}\mathrm{}(d,p)\mathrm{}$ has been obtained by observing the intensity of the beta-rays from ${\mathrm{B}}^{12}$ as a function of bombarding voltage from about 0.3 to 1.85 Mev. No resonance structure was observed in this region of bombardment. The yield at 1.47 Mev is approximately ${10}^7$ beta-rays/microcoulomb of deuterons.

The short-range protons which are formed in the above reaction were also observed in photographic plates, and range measurements showed that the $Q$-value of the reaction is 0.15 Mev. It is believed that this value does not represent the formation of ${\mathrm{B}}^{12}$ in its ground state, however, but in an excited state at about 1.1 Mev. A group believed to be protons of higher energy (corresponding to $Q=1.25\mathrm{}$ Mev) but of much lower intensity was subsequently observed.

It was shown, by bombardment of enriched ${\mathrm{B}}^{10}$ and of normal boron, that a gamma-ray of approximately 1.1 Mev energy is associated with the disintegration of ${\mathrm{B}}^{11}$ by deuterons. It is therefore almost certain that this gamma-ray arises from the decay of ${\mathrm{B}}^{12}$ to its ground state. Intensity measurements also indicate that this is the case.

• Received 27 June 1949

DOI:https://doi.org/10.1103/PhysRev.76.1150