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Emission Spectra of Gases

The emittance, often called the emissivity, of a sample at any wavenumber, e(v), is defined as the ratio of the radiant power emitted by a sample at a given temperature and the corresponding radiant power that would have been emitted by a blackbody source with the same geometry at the same temperature. (Strictly speaking, the term emissivity refers to a fundamental physical quantity, whereas emittance refers to a [Pg.363]

Fourier Transform Infrared Spectrometry, Second Edition, by Peter R. Griffiths and James A. de Haseth Copyright 2007 John Wiley Sons, Inc. [Pg.363]

If the reflectance of a sample is low, as it is with gaseous samples, e(v), is approximately equal to 1 — r(. Thus, for any sample for which a transmittance spectrum with discrete absorption bands can be measured, the emittance spectmm should yield equivalent information. As a result, qualitative analysis of the components of hot gases by infrared emission spectroscopy can be as easy as it is by transmission spectrometry. The problem of obtaining quantitative information by infrared emission spectroscopy is more difficult, since not only must the temperature of the sample be known if the radiant power from the blackbody is to be calculated, but the instrument response function must also be taken into account [1]. [Pg.364]

In many cases, the contribution of the surroundings, /e(v), to the measured spectmm, /s(v), must also be compensated [3]. The spectmm of the sample corrected [Pg.364]

Once the absorbance is known, the concentration can be calculated by a simple application of Beer s law. [Pg.366]


The study of the absorption and emission spectra of gases confirms, and in some respects extends, the information about molecular motions provided by the considera-... [Pg.18]


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