A statistical approach for simulating detailed-line spectra

A general statistical model for simulating electric-dipolar lines in complex spectra of LTE or NLTE plasmas is presented. In this model, each transition array is represented by a pair of Gaussian subarrays, whose characteristics ( average wavenumbers, strength distributions, and numbers of lines) change in a continuous way from LS ( where one subarray vanishes) to j j coupling. The transition amplitude and the two-level energies of each line are picked at random in a joint triple distribution that takes into account the correlation between the line strengths and energies. This insures that the first and the second strength-weighted moments of the line energies are equal to those obtained in the DLA approach. Examples of application to the calculation of Rosseland and Planck mean opacities are given ( Fe plasma in LTE, for T-e = 20 eV and P = 10(-2), 10(-3), 10(-4) g cm(-3)) which show very good agreement with the OPAL values.