SHIFT AND WIDTH OF HE-II LINES

Based on a quantum statistical many-particle theory, the shift and the width of some He II lines have been evaluated. Ion dynamics have been treated within the model microfield method. Furthermore, fine structu re splitting has been taken into account in order to check whether thi s effect is the cause for the existing large discrepancies between the oretical and experimental line widths. Besides the electronic contribu tions to the line shift, the shift due to the inhomogeneities of the i onic microfield as well as that due to the quadratic Stark effect has been included. (C) 1998 Elsevier Science Ltd. All rights reserved.