A method for calibrating vacuum-ultraviolet monochromators for measurement of absolute radiation intensities is described. It is based on calculating the brightness of an optically thin spectral line in the far ultraviolet from the brightness of a visible line originating from the same upper level. A grazing incidence monochromator and a Seya-Namioka monochromator were calibrated at a number of wavelengths between 1640 and 231 Å, using line pairs of hydrogen and ionized helium. Light sources used to obtain these lines are described. Problems of measurement and sources of error, particularly in the case of hydrogenlike spectra, are discussed.
EINAR HINNOV and FRITZ W. HOFMANN, "Measurement of Absolute Radiation Intensities in the Vacuum-Ultraviolet Region," J. Opt. Soc. Am. 53, 1259-1264 (1963)