Galactic Deuterium and its Energy Spectrum above 20 MeV per Nucleon

The fluxes and energy spectra of deuterium, protons, and helium were measured on the IMP-III satellite at a time near minimum solar activity. The deuterium differential energy spectrum in the range 17-63 MeV/nucleon is ∝E⁺² and, at 60 MeV/nucleon, the relative abundance ratios are H²/He⁴=0.15 and H²/H¹=0.05. If present values of experimental cross sections for the production of H² from nucleon interactions with He⁴ are used, the observed deuterium abundance may be accounted for by the traversal of He⁴ through 4 to 6 g/cm² of matter in cosmic-ray sources and the interstellar medium.