Toward standardization of Raman spectroscopy: Accurate wavenumber and intensity calibration using rotational Raman spectra of H-2, HD, D-2, and vibration-rotation spectrum of O-2

Abstract

Wavenumber and intensity calibration of a Raman spectrometer is performed with the use of pure rotational Raman bands(Delta nu = 0, Delta J = +/- 2) of H-2, HD, D-2, and vibration-rotation Raman bands (Delta nu = 1, Delta J = +/- 2) of O-2 as primary standards. Wavenumber calibration is based on reference transition wavenumbers available from accurate theoretical and experimental results. Intensity calibration is based on ratios of accurate theoretical Raman intensities for transitions from common rotational states to eliminate temperature effects. Polarization dependence is corrected to ensure that all of these bands have the correct depolarization ratio, rho = 0.75. The calibrated Raman spectrometer is used to measure standard Raman spectra of carbon tetrachloride, benzene, cyclohexane, toluene, and benzonitrile, for which the relative Raman intensities and depolarization ratios are determined with carefully estimated uncertainties. Vibrational frequencies of indene used for routine wavenumber calibration are updated.