Calibration of the absolute spectral response of Raman spectrometers

Abstract

A system for the calibration of the absolute spectral response of spectrometers is described using a standard reflector -of the type used especially for colour measurements -as a secondary light source. In contrast to conventional light sources for calibrations, the radiance is approximately constant over the whole area of the source, and the angular characteristic is known for a large range of reflection angles p. A special advantage is that the angular characteristic follows closely the Lambert-cosine-law in the region q-45". The radiant flux can be calculated exactly for various experimental conditions, especially for Raman spectroscopy.

Method for the measurement of absolute Raman scattering cross sections of crystalline powders

“…The measurements are made with a spectrometer, the absolute spectral response of which is calibrated by the procedure described in [9]. There are no optics between slit and the sample and the slit-sample distancz is so large that the monochromator 'sees' the total surface of the sample.…”

“…There are no optics between slit and the sample and the slit-sample distancz is so large that the monochromator 'sees' the total surface of the sample. Therefore, the monochromator is not completely illuminated and this must be taken into account in the calibration process [9].…”

“…The radiant intensity I(@) is calibrated relative to the radiant intensity of a standard light source [9]. Obviously, the condition e=O for the radiation measured by the spectrometer holds exactly only for radiation emerging from the centre of the sample.…”

“…In this paper a procedure for the measurement of absolute Raman scattering cross sections of crystal powders is described which is based upon this theory and which uses the special conditions of excitation by lasers. The intensities are measured with a spectrometer which is calibrated by the procedure published by D'Orazio and Schrader in this Journal [ 9 ] .…”

Reverse Intensity Correction for Raman Spectral Library Search

“…Earlier methods developed to standardize Raman spectral relative intensities used white light irradiance sources. 3 – 5 McCreery’s group pioneered the work of using luminescent glass as a convenient source that can easily reproduce the sampling condition. 6 – 8 This methodology was later adopted by the National Institute of Standards and Technology (NIST), 9 which now produces certified luminescent glass relative intensity standards for various excitation wavelengths.…”