Contribution of strong interactions to the wings of hydrogen lines broadened by the charged particles in plasmas

Abstract

The adiabatic theory applied in a reference system rotating with the perturbing field is used to describe the interaction between a hydrogen atom and a particle with charge Z pe . The time development operator T( t) obtained is exact for the no-quenching dipolar term to which the weak interactions are reducible. We have shown that this solution constitutes a good approximation for the treatment of the strong interactions which involve in addition the no-quenching quadrupolar term and the dipolar term connecting states with different principal quantum numbers. For the first well separated hydrogen lines ( n ⩽ 4) and the usual plasma spectroscopy temperatures ( T ≅ 10 4°K), it is found that the non-adiabatic effect does not exceed a few per cent. Within the framework of the one perturber approximation, the correlation function of the line wings is expressed by means of the phase shift and the intensity of the various components. These two parameters are time-dependent through the rotation angle φ ( t) and the instantaneous scalar distance R ( t) of the perturber with respect to the radiating atom. As an example, the detailed numerical calculation has been performed for the Lyman-α line. In addition to an increase of the broadening effect, we note the striking asymmetry effect due to the strong electron interactions. In the intermediate spectral region, the asymmetry favours the red wing and must be added to that coming from the ions. Farther into the line wings, where the central component no longer contributes, the electron asymmetry tends to change sign and to cancel the ion asymmetry partially. Comparison has been made of our theoretical results with the theoretical and experimental results given by other authors. Particularly satisfactory agreement has been obtained with the experimental data given by Elton and Griem for the Lyman-α red wing ( N = 3·6 × 10 17 cm -3, T = 2·04 × 10 4°K). The same is true with the experimental data of Boldt and Cooper ( N = 8·4 × 10 16 cm -3, T = 1·22 × 10 4°K) if the electron density is assumed to be lower.