Gamma-Rays from Alpha-Particle Reactions

Gamma-rays from sodium, magnesium, aluminum, silicon, phosphorus, and sulfur targets under cyclotron bombardment by 7-Mev alpha-particles have been observed. Energies were obtained by measuring the maximum range of Compton-recoil electrons in aluminum, using two beta-ray counters in coincidence. The following gamma-ray energies were found: sodium, 1.85±0.15 Mev and 2.80±0.25 Mev, with an intensity ratio of 6 to 1; magnesium, 1.8±0.2 Mev and 4.3±0.3 Mev, with an intensity ratio of 3 to 1; aluminum, 3.5±0.3 Mev; silicon, 2.3±0.3 Mev; phosphorus, 2.55±0.25 Mev and 4.1±0.4 Mev, with an intensity ratio of 8 to 1; sulfur, 2.4±0.3 Mev. In cases where correlation can be made with energy levels given by the corresponding $\alpha p$ reactions the transition from the second excited state to ground in the product nucleus seems to be favored.