Vibration–rotation spectra of HCl solutions in SF 6 at isochoric conditions

Abstract

We report here new data on the fundamental and the first overtone band shapes measured in the IR spectra of HCl solutions in SF 6 at several constant densities in the range of ρ∼220–260 amagat and at temperatures T∼280–340 K, i.e. below and above the critical point of the solvent. The experimental data will be discussed in terms of a recently developed ‘modified rotor’ model, that assumes solute species to rotate in a quasi-free manner once their rotational and translational kinetic energies exceed the barrier to rotation caused by a slowly varying anisotropic potential of interaction between the solute and solvent molecules.