Cross sections for production of the 15.10-MeV and other astrophysically significant gamma-ray lines through excitation and spallation of /sup 12/C and /sup 16/O with protons

The ratio of the flux of 15.10-MeV gamma rays to the flux of 4.438-MeV gamma rays resulting from excitation of the corresponding states in /sup 12/C is a sensitive measure of the spectrum of the exciting particles produced in solar flares and other cosmic sources. These gamma rays are produced predominantly by interactions with /sup 12/C and /sup 16/O, both of which are relatively abundant in the solar photosphere. Gamma-ray production cross sections for proton interactions have been reported previously for all important channels except for the production of 15.10-MeV gamma rays from /sup 16/O. The first reported measurement of the 15.10-MeV gamma-ray production cross section from p+ /sup 16/O is presented here. A cyclotron was employed to produce 40-, 65-, and 85-MeV protons which interacted with CH2 and BeO targets. The resultant gamma-ray spectra were measured with a high-purity germanium semiconductor detector at 70, 90, 110, 125, and 140 deg relative to the direction of the incident beam for each proton energy. Other gamma-ray lines resulting from direct excitation and spallation reactions with /sup 12/C and /sup 16/O were observed as well, and their gamma-ray production cross sections, several of which have not been reported previously, are presented. The results are compared with previously reported measurements, as available