The gamma-ray yield from ${\mathrm{Al}}^{27}$ bombarded with 0.5 to 1.4 Mev protons has been investigated with a sensitive G.M. counter. By introduction of a "cutter" device which automatically stopped the measurements when the voltage deviated more than a certain amount from the desired value, a resolving power of 4 kev was obtained. Under this condition a number of previously known peaks have been resolved into groups of narrow lines. In the investigated region the proton width has been estimated to be less than 1 kev, and a rough estimate of the efficiency of the gamma-ray counter gave a radiation width of the order of 1 ev.

• Received 29 January 1947

DOI:https://doi.org/10.1103/PhysRev.71.661