High-Resolution Raman Spectroscopy of Gases with Laser Sources, V* Use of the Single-Mode Argon Laser†

A description is presented of an experimental method of obtaining Raman spectra of low-pressure gases under high resolution. The technique utilizes a single-mode argon laser, a multiple-pass Raman cell located inside the laser cavity, and baked Kodak IIIa-J photographic plates. A method is described which uses the single-mode Fabry–Pérot étalon to change the wavelength of the exciting line so as to compensate for changes of the dispersion of the spectrograph brought about by variations of barometric pressure. Rotational Raman spectra of heavy polyatomic molecules can now be photographed at room temperature with a resolution determined by the pressure and Doppler broadening of spectrum lines.