Measurement of the Stark broadening parameters of several Ar II lines

The profiles of several electron-impact-broadened Ar II lines emitted by a high-density Z-pinch plasma have been recorded using a rapid scanning Fabry-Pérot interferometer. The plasma electron density was determined by Fabry-Pérot interferometry in conjunction with a laser light source. Measurement of the relative intensity of an Ar III line and a nearby Ar II line enabled the plasma temperature to be estimated. The measured Ar II linewidths are compared with those predicted by the impact approximation using straight-line perturber orbits and neglecting lower-state broadening. In all cases studied the ratio of experimental to theoretical linewidth was at least a factor of 2. The cause of these large discrepancies, and the implications of the results for other emitting species, are to be discussed in a subsequent paper.