Non-LTE opacity calculations with n-l splitting for radiative hydrodynamic codes

We present a new method for calculating opacities in a non-LTE plasma, based on modeling of the one-electron atomic potential in the framework of the "average atom" approach. In this model, the collisional-radiative equations of an average ion are solved and the resulting screened charges are used to reconstruct the one-electron atomic potential. Average atom wave functions, oscillator strengths and Slater integrals are calculated by quantum mechanics in the reconstructed potential. Dipolar matrix elements have improved values compared to hydrogenic formulas, especially for orbitals close to the ion core. Configuration accounting is done using the independent electron approximation and perturbation theory. Our method, compared to previous LTE average atom calculations gives realistic values of plasma opacities, especially in the soft x-ray range where the Delta n = 0 transitions play an important role. A comparison of radiative hydrodynamics simulations performed with opacities calculated in the n and n-1 representation shows significant differences. (C) 1997 Published by Elsevier Science Ltd. All rights reserved.