The rovibrational Raman spectrum of toluene vapour at a pressure of 3 kPa was recorded photoelectrically at medium resolution. The sample was contained in a Brewster angle cell in the cavity of the argon ion ring laser of a CARS spectrometer, the scattered light being transferred to the Raman spectrometer by a fibre-optic bundle. Nine fundamental bands, eight a,' and one uj", and some overtone bands were observed and assigned.

A continuous-wave CARS spectrometer was equipped with a new frequeucy-stabilized argon ion ring laser and better stabilization for the tunable dye laser was introduced. Special quartz sample cells witb Brewster angle windows were placed in the focal region of the argon ion ring laser. A new data acquisition system was installed which allows the simultaneous retording of CARS signals and calibration spectra and the subsequent evaluation of the data. An instrumental resolution of less than 0.001 em-' and a wavenumber accuracy of about f0.006 cm-' were achieved. As an example of the performance of the spectrometer, the CARS spectrum of ethane was measured in the region of the CH vibrations at pressures between 95 and 1.9 kPa. The spectra were compared with the stimulated Raman spectrum published recently.

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