A study of molecular rotation in dense fluids from the first vibrational overtone band shape of HCl in Xe fluid

Abstract

Spectral profiles of the (2 ← 0) vibration-rotation band of HCl dissolved in fluid Xe are recorded in the 267–333 K temperature range at a constant density of 345 Amagat and compared with predictions of an earlier developed modified rotor theoretical model [Bulanin et al. PCCP, 2003, 5, 285]. An improved agreement with the measured distributions is demonstrated in the range of the P- and R-branches. The results obtained are compared with previous analyses of the (1,2 ← 0) bands in HCl–SF₆ and (1 ← 0) band in HCl–Xe systems. The observed behaviour of the separated central Q-branch is consistent with the presence in the fluid of long-lived solute–solvent spatial correlations caused by the anisotropy of the binary interaction potential, which in a low-density limit leads to formation of van der Waals complexes.