An expression for the shape of an infra-red absorption line is developed on the basis that the principal factor in the broadening of a line is the limitation of the length of wave train a molecule may absorb due to its perturbation by thermal collisions. The shape of the line is accordingly found by expanding the finite wave train with a Fourier integral and then integrating over the distribution of lengths of wave train given by the kinetic theory of gases. The absorption coefficient as found in this way may be expressed to a high approximation by means of two damping curves involving the number of molecules per unit volume, the temperature, and σ the effective diameter.To apply this result to the analysis of observed infra-red spectra allowance must be made for the low spectrometer resolution due largely to the wide slits employed. Two expressions are developed, holding for all but very weak lines, which relate the area under the absorption line Abs, the minimum value of the transmis

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wave damping curves infrared absorption line kinetic theory of fourier integral analysis of observed infrared spectra

David M. Dennison,.The Shape and Intensities of Infra-Red Absorption Lines. 31 (4),503–519.

David M. Dennison,"The Shape and Intensities of Infra-Red Absorption Lines" 31

David M. Dennison,"The Shape and Intensities of Infra-Red Absorption Lines"