The slit function of a double monochromator has been studied using a dye laser and a few ion laser lines. The value of the slit function is about 9 orders of magnitude below the peak at 300 nm from the line center. The difference between the slit function obtained by the monochromator scanning over a fixed spectral line and that obtained by tuning a spectral line through a fixed monochromator setting is found to be negligible for all but the most demanding applications. Also reported is a prominent structure in the slit function which is attributed to the intermediate slit of the instrument.
Robert D. Saunders and John B. Shumaker, "Apparatus function of a prism-grating double monochromator," Appl. Opt. 25, 3710-3714 (1986)