Investigation of the wavelength accuracy of Brewer spectrophotometers

The wavelength accuracy of the Brewer spectrophotometer in the 280-360-nm s pectral range is improved by a new grating-drive mechanism and a new disper sion function derived from the Brewer geometry. With the new mechanism, the reproducibility of wavelength settings for spectral emission lines is bett er than 0.3 pm (0.0003 nm) and, with a thermally compensated version, the e ffect of temperature is less than 0.4 pm K-1. The new dispersion function f its spectral line positions better than the standard function and is less p rone to extrapolation error. Applying the new function to data from four ne w and ten standard drives shows that the new drives perform as well as the best of the standard ones and much better than the majority. (C) 1998 Optic al Society of America.