%0 Journal Article
%T Molecular Laser Spectroscopy as a Tool for Gas Analysis Applications
%A Javis Anyangwe Nwaboh
%A Thibault Desbois
%A Daniele Romanini
%A Detlef Schiel
%A Olav Werhahn
%J International Journal of Spectroscopy
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/568913
%X 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. 1. 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¨C7]. Molecular spectroscopy as performed by probing intra- and intermolecular vibrational transitions and further underlying rotational substructure has been used to study and illuminate bond structures and formation of atomic and molecular agglomerates and clusters [8, 9]. These techniques are applied due to the absorption, emission, or scattering of electromagnetic radiation by atoms or molecules. The choice of each of these physical phenomena, for example, absorption, for molecular species quantification or qualification, depends on the intended application. Absorption spectroscopy, for instance, is employed to identify and quantify molecular species in gas analysis applications such as remote sensing, atmospheric monitoring, vehicle exhaust emissions, or even exhaled breath gas tests [10¨C28]. In metrology, molecular absorption spectroscopy could be used to assign amount fractions (concentrations) to species in gas mixtures of known molecular constituents (Note, for a clarification of different terms in use see e.g.: http://goldbook.iupac.org/A00296.html). The determination of the amount fraction of a species without the use of calibrated reference gas mixtures, leads to the so-called ¡°calibration-free¡± infrared spectrometry. Calibration-free means the amount of substance fraction of a species is measured in terms of the International System of Units (SI) derived unit mol¡¤mol£¿1 without referencing to a standard or a measurement expressed in the same unit [29]. The desire to derive amount fraction results by means of spectroscopy that are directly traceable to the SI triggered the idea of a traceable infrared laser spectrometric amount fraction measurement
%U http://www.hindawi.com/journals/ijs/2011/568913/