A New Method for the Calibration of the Spectral Sensitivity of a Raman Spectrometer

Abstract

The calibration of the relative spectral sensitivity of a Raman spectrometer is usually done by comparison of the curve of spectral irradiance (E—1) of a standard lamp with the intensity of the signal (I—1) of the same lamp when registered by the spectrometer. Although this method is in theory accurate, there are some types of experimental errors concomitant with it. Those arise mainly from the different optical arrangements used in the calibration of the spectrometer and in the registration of the Raman spectra. For example, if the filament is put in the theoretical place where the Raman scattering takes place, zones of different color temperature can be focused on the entrance slit of the spectrometer, since the magnification of the collecting system is usually greater than 3 and the filament is, furthermore, larger than the slit. If a pinhole is used instead of the filament then the angular dependence of the light behind the pinhole can be altered by diffraction effects. If a diffuse reflector is used, it has to be calibrated previously, because of the deviations of the Lambert law that show the actual standard reflectors, etc.