Detection of 6.13 MeV gamma-rays within and at the top of the atmosphere

A measurement of the 6.13 MeV gamma-radiation from excited O-16 in the atmosphere has been made with a high-resolution Ge(Li) spectrometer flown from Palestine, Texas, 1974 June 10, on a high-altitude balloon. This measurement, made both within and near the top of the atmosphere, is found to have the same general profile as predicted by a semiempirical model, but gives a flux about a factor of 2 higher than predicted. Certain variations in the intensity at float altitude have led to the hypothesis of an extraterrestrial source of 6.13 MeV gamma-radiation from the galactic anticenter. The 3 sigma upper limits for a number of other astrophysically significant line fluxes are also given. The data presented here are consistent with either a source or a no-source hypothesis.