A method has been developed for finding the half-intensity width, to an accuracy of ±5%, of the profiles of spectral lines photographed in the vacuum ultraviolet. Plate calibration is achieved by an aperture restriction device placed at the Sirks focus of a 3-meter normal incidence vacuum spectrograph. This gives a stepped intensity in the focal plane with a standard ratio of 2:1. The measurement is not affected by reciprocity law failure or intermittency effect in the photographic emulsion, and can be used with pulsed light sources.
B. B. Jones, "A Method for Obtaining Accurate Half-Intensity Widths of Spectral Lines Photographed in the Vacuum Ultraviolet," Appl. Opt. 1, 239-242 (1962)