Molecular Laser Spectroscopy as a Tool for Gas Analysis Applications

Javis Anyangwe Nwaboh,Daniele Romanini,Thibault Desbois,Detlef Schiel,Olav Werhahn

doi:10.1155/2011/568913

Abstract

We have used the traceable infrared laser spectrometric amount fraction measurement (TILSAM) method to perform absolute concentration measurements of molecular species using three laser spectroscopic techniques. We report results performed by tunable diode laser absorption spectroscopy (TDLAS), quantum cascade laser absorption spectroscopy (QCLAS), and cavity ring down spectroscopy (CRDS), all based on the TILSAM methodology. The measured results of the different spectroscopic techniques are in agreement with respective gravimetric values, showing that the TILSAM method is feasible with all different techniques. We emphasize the data quality objectives given by traceability issues and uncertainty analyses.

Highlights

Throughout the last years many molecular laser spectroscopic techniques have been used to qualify and quantify different physical mechanisms taking place in atoms or molecules [1,2,3,4,5,6,7]
We report results performed by tunable diode laser absorption spectroscopy (TDLAS), quantum cascade laser absorption spectroscopy (QCLAS), and cavity ring down spectroscopy (CRDS), all based on the traceable infrared laser spectrometric amount fraction measurement (TILSAM) methodology
We focus on the use of the TILSAM method to perform absolute concentration measurements of molecular species using different laser spectroscopic techniques

Summary

Introduction

Throughout the last years many molecular laser spectroscopic techniques have been used to qualify and quantify different physical mechanisms taking place in atoms or molecules [1,2,3,4,5,6,7]. Other spectrometric techniques, such as quantum cascade laser absorption spectroscopy (QCLAS) or cavity ring-down spectroscopy (CRDS), can be used to perform absolute amount fraction measurements based on TILSAM. A possible discrepancy between the spectrometrically derived amount faction of (87.3 ± 4.6) μmol·mol−1 and that of the nominal value could not be exactly quantified and further evaluated at the time this paper was prepared, because the sample was taken from an ongoing comparison for which exact reference values were not yet available These QCL results were presented here, to demonstrate the application of the TILSAM method to intrapulse QCL spectrometry. The lower limit of 2% of the line strength uncertainty was taken for this uncertainty analysis knowing that the amount fraction uncertainty was to be increased once the higher limit had to be used

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