The Production of Deuterium in Supernova Shocks

A strong shock in the stellar envelope of a Type II supernova speeds up in the density gradient. Because of the low density, the equilibrium temperature behind the shock may be relatively low- a few times 10? the high relative nuclear kinetic energy (Ei) up to many MeV per nucleon. The radiation equilibrium mechanisms, bremsstrahlung and inverse Compton scattering, are slow compared with ion-ion thermalization. Consequently, a high-temperature ion precursor forms (kTi - %E1) that lasts for 100 E6l/2 (Ei in MeV) Thomson-scattering periods (1/ne c) sufficient to allow from 60 to 90 proton-alpha and alpha-alpha collisions at E 10 MeV. This is the minimum energy at which the aIphas will be spalled to free neutrons and protons. Subsequent capture of the neutrons by the protons is assured at a low enough equilibrium temperature that the deuterium survives and is ejected. A shock strength of 10 MeV per nucleon should occur at a mass fraction of a few times 10- , producing a fraction of a few times 10- deuterium per supernova. A processing of 10 percent of the galactic mass through Type II supernovae is adequate to produce the observed deuterium. Subject headings:abundances - nudear reactions - shock waves - supernovae