FAR-INFRARED SPECTRA OF HCL IN DENSE AR AND TIME-DEPENDENT ANISOTROPIC POTENTIAL AUTOCORRELATION FUNCTIONS - A MOLECULAR-DYNAMICS STUDY

In many spectral theories, the knowledge of the time autocorrelation f unctions associated with the solute-solvent intermolecular anisotropic potential is a necessary step to obtain the far-infrared (FIR) spectr a of small polar diatomic molecules dissolved in a nonpolar solvent. W ithin the pairwise additive approximation, we have obtained these func tions from a molecular dynamics simulation for HCI in fluid Ar (betwee n 100 and 480 amagat) at T = 162.5 K. The simulated correlation functi ons are tested in the calculation of the pure far-infrared spectrum, a ppropriately described by a theory incorporating memory effects, line mixing effects, and the influence of any anisotropy order on the diato m-atom intermolecular potential. The comparison between the theoretica l and experimental spectra allow us to obtain some conclusions about t he relative importance of the first and second order anisotropic inter action correlations on the FIR spectra of HCI in dense Ar.