Estimates of Dielectric Shifts in Infrared Spectra of Pure Liquids for Use in the Theoretical Evaluation of Vapor Pressure Isotope Effects

Abstract

Abstract Observed fundamentals in infrared spectra of pure liquids are red-shifted by the so-called "dielectric effect". This dielectric shift is an excited state effect, and the observed fundamentals must be corrected before one deduces the isotope effects on the zero-point vibrational energy which are needed in the theoretical evaluation of vapor pressure isotope effects. A simple formula is applied to calculate the dielectric shift, which requires only the molar concentration and the integrated absorption coefficient for the fundamental.