Abstract

Several techniques of exciting Raman spectra of low-pressure gases and vapors with cw laser radiation are described. Both the He–Ne laser with output at 6328 å and the Ar⁺ ion laser with output at 4880 and 5145 å have been used. The use of the He–Ne laser with a multiple-pass Raman tube inside the laser cavity yields Raman spectra which can be photographed in exposure times that are equivalent to those required with the classical Hg-arc and large-volume Raman tube as the source of scattered radiation. The Ar⁺-ion laser allows the photoelectric recording of rotational Raman spectra at atmospheric pressure with a signal/noise ratio of 10:1 when the Raman tube is located outside the laser cavity, and about 100:1 when the Raman tube is inside the laser cavity. A comparison is given for the relative efficiency when the scattering gas is located inside and outside the laser cavity. Pure rotational Raman spectra for N₂, O₂, CO₂, and H₃CC≡CH (methylacetylene) are presented. The depolarization ratios of both the Rayleigh and Raman lines of N₂, O₂, and CO₂ have been determined and relative scattering cross section for the pure rotational Raman scattering of oxygen has been obtained.

© 1967 Optical Society of America

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

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High-Resolution Raman Spectroscopy of Gases with Laser Excitation*

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