Ionization by High-Energy Particles and the Electron Scattering Opacity in Supernovae

Ionization equilibrium equations appropriate for supernova atmospheres are described. The solution of these equations indicate the high-energy particles associated with radioactive Ni-56 and Co-56 decay sustain a significant degree of ionization in the supernova plasma. Under certain physical conditions, the resulting electron scattering opacity can be many orders of magnitude greater than LTE estimates predict. A straightforward application of the present results to standard (diffusion approximation) hydrodynamic computations is proposed in which the non-LTE electron scattering opacity is expressed in terms of the local radioactive decay energy deposition rate and the mass density. Application to an analytic supernova dynamic evolution computation is presented to illustrate the results expected from more detailed calculations.