Time-dependent hydrogenic ionization model for non-LTE mixtures

We present an efficient, non-local thermodynamic equilibrium (non-LTE), time-dependent ionization model for laser-produced plasmas containing mixtures of elements (species). An ionization distribution for each species which is consistent with the ambient electron density is obtained by use of an iterative procedure. Energy levels for each shell having a given principal quantum number and for each ion stage of each species in the mixture are calculated using screening constants. Steady-state non-LTE as well as LTE solutions are also provided. The model is particularly useful at low temperatures where convergence problems are usually encountered. Our results compare well with previously published data for selenium. We apply our model to typical situation in X-ray laser research and laser-produced plasmas. We illustrate the application to mixtures by calculation an approximate ionization for fused quartz at solid density and compare the results with previous calculations. (Copyright (c) 1999 Elsevier Science B.V., Amsterdam. All rights reserved.)