Quantitative characteristics of methane’s infrared spectra

Xian-yong Liu; Li-ping Shang; Hong-lei Li

doi:10.1117/12.571742

28 January 2005 Quantitative characteristics of methane's infrared spectra

Xian-yong Liu, Li-ping Shang, Hong-lei Li

Proceedings Volume 5646, Nonlinear Optical Phenomena and Applications; (2005) https://doi.org/10.1117/12.571742
Event: Photonics Asia, 2004, Beijing, China

Abstract

FTIR spectra have been widely used in quantitative analyses of mixed gases. Although Beer's Law regulates the relationships between absorbency and the product of concentration and path length, its deviations have been found rather complicated. Here we present the complexity of quantitative relationships between methane's infrared spectra and concentrations and resolutions. Measurements of the same methane sample's spectra under different resolutions demonstrate that both area absorbency and height absorbency vary with resolutions; spectra at lower resolution have bigger area absorbency for most of the peaks and are more likely to saturate for peaks of strong absorption. Standard methane sample of certain concentration is diluted with super pure nitrogen via mass control flowmeters and continuously passes through a 2-meter gas cell, such that the spectra of methane of different concentrations are collected. The area absorbencies of different peaks are carefully calculated via OMNIC software and results show that peaks with lower absorption are more likely to fit to linearity but more reluctant to changing concentrations. Area absorbencies are integrated through characteristic absorption regions, height absorbencies and area absorbencies are calculated at the two main absorption peaks and measurements show that approximative linearity fits all the areas and the best linearity appears at 1035.6cm^-1.

Citation Download Citation

Xian-yong Liu, Li-ping Shang, and Hong-lei Li "Quantitative characteristics of methane's infrared spectra", Proc. SPIE 5646, Nonlinear Optical Phenomena and Applications, (28 January 2005); https://doi.org/10.1117/12.571742

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