Calculation of the Lyman-α asymmetry in a dense,partially-ionized hydrogen plasma

The asymmetry of the hydrogen resonance line Lyman-α is calculated. The electron perturbers are treated by the impact approximation and the ion perturbers by the quasistatic approximation. Contributions to the quasi-static ion broadening from first- and second-order asymmetry terms are included in the calculations, i.e. contributions from the quadrupolar ion-atom interaction and the quadratic Stark effect.The asymmetry at small separations from the line centre is unaffected by the inclusion of the second-order correction and remains slightly larger than the experimentally determined asymmetry. At larger separations from the line centre, the inclusion of the second-order correction causes a decrease in asymmetry due primarily to the quadratic Stark effect. For these larger separations from the line centre, rather poor agreement is obtained between theory and the experimental results of Boldt and Cooper.