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Accurate intensity calibration for low wavenumber (−150 to 150 cm −1 ) Raman spectroscopy using the pure rotational spectrum of N 2
Author(s) -
Okajima Hajime,
Hamaguchi Hiroo
Publication year - 2015
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.4731
Subject(s) - raman spectroscopy , wavenumber , intensity (physics) , calibration , chemistry , spectral line , coherent anti stokes raman spectroscopy , analytical chemistry (journal) , spectrometer , diatomic molecule , calibration curve , molecular physics , nuclear magnetic resonance , atomic physics , raman scattering , optics , physics , molecule , organic chemistry , chromatography , quantum mechanics , astronomy , detection limit
We report on an accurate intensity calibration method for low wavenumber Raman spectroscopy. It uses the rotational Raman spectrum of N 2 . The intensity distributions in the rotational Raman spectra of diatomic molecules are theoretically well established. They can be used as primary intensity standards for intensity calibration. The intensity ratios of the Stokes and anti‐Stokes transitions originating from the same rotational levels are not affected by thermal population. Taking the effect of rotation–vibration interactions appropriately into account, we are able to calculate these intensity ratios theoretically. The comparison between the observed and calculated ratios of the N 2 pure rotational spectrum provides an accurate relative sensitivity curve (error ~5 × 10 −4 ) in the wavenumber region of −150 to 150 cm −1 . We determine the temperature of water solely from the low wavenumber Raman spectra, using a thus calibrated spectrometer. The Raman temperature shows an excellent agreement with the thermocouple temperature, with only 0.5 K difference. The present calibration technique will be highly useful in many applications of low wavenumber quantitative Raman spectroscopy. Copyright © 2015 John Wiley & Sons, Ltd.