Plasma Broadening of Autoionizing Resonances

A general formulation is developed to study and quantitatively ascertain the effect of plasma broadening of intrinsic

autoionizing (AI) resonances in photoionization and electron-ion scattering cross sections. In particular, R-matrix data for iron ions described in a paper in the RMOP series (RMOP-II, hereafter RMOP2) are used to demonstrate underlying physical mechanisms due to electron collisions, ion microfields (Stark),

thermal Doppler effects, core excitations, and free-free transitions. Breit-Pauli R-matrix (BPRM) cross section for the large number of bound levels of Fe ions are

considered, 454 levels of Fe~XVII, 1,184 levels of Fe~XVIII and 508 levels of Fe~XIX. Following a description of theoretical and computational methods, a sample of results is presented to show significant broadening and shifting of AI resonances due to extrinsic plasma broadening as a function of temperature and density.

Redistribution of AI resonance strengths broadly preserves their integrated strengths as well as the naturally intrinsic asymmetric shapes of resonance complexes which are broadened, smeared and flattened, eventually dissolving into the bound-free continua. The impact on plasma opacities is discussed.