Abstract

A laser resonance absorption spectrometer is used to investigate the characteristics of both self and nitrogen collision broadened carbon dioxide in resonance with He–Ne laser radiation at 4.2 μm. The absorption coefficient in these broadening conditions has contributions from the R(28) to R(34) absorption lines of the ν₃ CO₂ spectrum. The Fletcher-Powell optimization method is used to reduce the raw absorption data and to find the best value average collision broadening coefficient and laser emission frequency for a Lorentzian line shape model of the contributing lines. Pure carbon dioxide absorption in a pressure range of from 0.0016 atm (1.25 Torr) to 0.33 atm (250 Torr) is described well by the model with an average self broadening coefficient of 0.084 ± 0.008 cm⁻¹ atm⁻¹ for laser frequencies located at either 2370.591 ± 0.020 cm⁻¹ or 2371.135 ± 0.019 cm⁻¹. Nitrogen broadened carbon dioxide in the total pressure range of from 0.13 atm (100 Torr) to 1.18 atm (900 Torr) is characterized by the same model with the laser frequency at 2371.102 ± 0.023 cm⁻¹ and average nitrogen broadening coefficient of 0.067 ± 0.007 cm⁻¹ atm⁻¹. The average absorption coefficient for low concentrations of carbon dioxide in a 1-atm total pressure nitrogen environment has been determined experimentally as 9.90 ± 1.49 cm⁻¹ atm⁻¹. All the listed results are at 296 K.

© 1989 Optical Society of America

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