Line radiation from a hot, optically thin plasma - Collision strengths and emissivities

Abstract

Theoretical and experimental data are collected for collision strengths of the strongest multiplets between 1 and 3000 A in a hot, optically thin plasma. The elements included are H, He, C, N, O, Ne, Mg, Si, S, and Fe. Simple power-law fits, as a function of gas-kinetic electron temperature, are provided for the collision strengths of the strongest multiplets for temperatures between 40,000 and 100 million K. The fits are good to about 10 percent for temperatures within a factor of 3 of the temperature at which the steady-state equilibrium ion abundance peaks. The collision strengths for these strong multiplets are also used to calculate the multiplet emissivities for a plasma assumed to be in steady-state collisional ionization equilibrium. The multiplet emissivities are given for temperatures between 2.5 million and 100 million K. The total steady-state emissivity (including continuum) and the emissivities in selected energy bins are also presented. Note, however, that steady-state collisional ionization equilibrium is not a good assumption for shock-heated plasmas for temperatures lower than about three million K.