Polarisation shift of low-Z Balmer lines in laser-produced plasmas

Using laser-produced plasmas of high temperature and density the authors have investigated the possible shifts due to local plasma polarisation on the H alpha lines emitted by C VI and N VII. In contradiction with a number of theoretical treatments, they have found no evidence for shifts of the predicted magnitude. Whatever the plasma conditions the H alpha lines have been observed to be unshifted to within +or-0.02 AA corresponding to the estimated accuracy of the measurements. Results are discussed in the light of the existing theoretical treatments and are compared with similar investigations in the isoelectronic sequences.