Dielectric effects on the spectra of condensed phases

The single-resonance damped oscillator model for molecular polarizability is combined with the Lorentz model for the local field in order to obtain expressions describing the dielectric constant and absorption coefficient of pure condensed phases. These expressions are functions of three parameters: the transition dipole matrix element, the molecular resonance frequency, and the lifetime. It is found that condensed phases exhibit a macroscopic resonance frequency different from the molecular resonance frequency, and equations are supplied whereby one may calculate this shift. The shape of the condensed phase absorption coefficient is found to be unsymmetrical about the resonance frequency for intense bands; a method is described in which one exploits this lack of symmetry in order to find the transition dipole matrix element. Attenuated total reflection data for four liquid phase infrared bands are analyzed in terms of the absorption model.