Precise measurement of the depolarization ratio from photoacoustic Raman spectroscopy

A new method for the accurate determination of the Raman depolarization ratio is reported with an improved setup for photoacoustic Raman spectroscopy (PARS). The precise measurement is achieved by measuring the dependence of the acoustic signal intensity on the cross-angle between the polarizations of two incident laser beams. We demonstrate this sensitive and simple method with several gaseous molecules,suchasCH4 andH2.Themeasuredresultsofdepolarizationratiosagreewellwiththetheoretical values with an upper error limit of ±0.005, which is comparable to that with polarization-resolved CARS spectroscopy. Copyright  2007 John Wiley & Sons, Ltd.

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