Determination of absolute Raman cross sections using the inverse Raman effect

✍ Scribed by Lester J. Hughes; Larry E. Steenhoek; Edward S. Yeung

• Publisher: Elsevier Science
• Year: 1978
• Tongue: English
• Weight: 432 KB
• Volume: 58
• Category: Article
• ISSN: 0009-2614
• DOI: 10.1016/0009-2614(78)85064-7

✦ Synopsis

1%~ use a giant-puke ruby laser and a cw dye laser in a unique inverse Raman spectrometer, and determined the absolu:e Rarnan cross section for the nitrobenzene line at 1345 cm-' to be (1.38 2 0.27) x 10" cm2 ST-'_ 1_ intraduc tion The determination of absolute l&man cross sections has long been a challenge to the spectroscopist. In addition to the otivious applications to the understanding of molecular scattering tensors [ 1 ] , these cross sections have found use in predicting stimulated Raman gain coefficients [2], in the determination of absolute two-photon absorption cross sections [3], and in predicting intensities in coherent anti-Stokes Raman scattering [4]. Raman spectrometers of the pre-laser era only allow relative scattering intensities to be recorded, because of the ill-defmed intensity of excitation and uncertainties in the interaction volume. Still, some absolute intensity standards have been suggested to overcome these difficulties_ Using Raman to Rayleigh intensity ratios [5] is a possibility, but is not reliable because of the presence of small-range order of the molecules in liquids and intermoIecular forces. The H2 J = 1 to J = 3 transition has also been suggested as an absolute intensity standard [6] because of the availability of theoretical predictions. Unfortunately, this cannot be used in liquids. Laser Raman intensity measurements [7,8] are not free from systematic errors either, the major ones being (i) the calibration of the response of the detector; i Research supported by the 'J.S. Department of Energy, Division of Bask Energy Sciences_