Correlation effects and their influence on line broadening in plasmas: Application to Hα

In the last two decades, several computational approaches for the Stark broadening in plasmas have been developed, where the motion of both ions and electrons is simulated and their fields are approximated by using an effective Debye–Yukawa potential. This approximation, in general, should be questioned when the number of plasma particles in the Debye sphere is about unity or below. For testing the applicability of this approximation, molecular-dynamics simulations were performed, with all plasma particles interacting by the Coulomb potential, and the correlations in the motion of the particles were analyzed. It was found that even for a moderately coupled plasma (Ne = 1018 cm−3, T = 1 eV, where the number of electrons in the Debye sphere is ≈1.7), the collective effects play a significant role in the statistical and dynamical properties of the microfields. Nevertheless, the corrections to the Hα profile are rather small. We also show that accounting for transitions with Δn ≠ 0 is crucial for proper determination of the shift, and to a lesser extent also of the width, of the spectral line.