A STATISTICAL APPROACH TO THE ANALYSIS OF INFRARED BAND PROFILES

Abstract

A method is described for the quantitative description of the profile and asymmetry of an infrared absorption band, based on the computation of the second and third incomplete moments of the absorbance curve. Provision is included for differentiation between the intrinsic band asymmetry and that induced by instrumental factors dependent on the direction of scan. A program has been prepared for an I.B.M. 1620 computer to facilitate the calculation of the moments. This program also yields the incomplete fourth moments, the statistical kurtosis parameter ([Formula: see text]), and the Gauss–Cauchy index, though these quantities are not employed in the present investigation. Examples are given of the application of these computations to the analysis of the effect of the spectral slit width on the profiles of bands at 812.7 and 726.6 cm−1 respectively in the spectra of carbon disulphide solutions of perylene and anthracene, and of the effect of the amplifier time constant on the asymmetry of the band at 2234.4 cm−1 in the spectrum of p-chlorobenzonitrile in tetrachloroethylene solution.