Laser spectroscopic studies of the P(7) subband of the v₃ band of methane

The P(7) subband of the v₃ absorption band of methane has been investigated by laser spectroscopoy techniques. An introduction to the infra-red vibration-rotation absrption bands of methane is given and other investigations of the v₃ band are discussed. A new method of stabilising the emission from a 3.392µ helium-neon laser has been divised using simple thermal control techniques. The stabilisation of the laser provided a source of monchromatic infro-red radiation capable of resolutions of the order of 10¯⁵ cm¯¹ . With the aid of the high resolving powers of the laser, high accuracy absorption data has been obtained over a wide range of pressures and temperatures. The lack of detailed comparisons of accurate experimental absorption coefficients with predictions from the theory is noted, and a brief review of the theory of absorption profiles which include the effects of several line broadening mechanisms is given. [...]