Spectroscopic and theoretical studies of the OCO⋯HF complex in pressurized gases

Abstract

The spectra of HF–CO₂ mixtures have been measured at T= 300 K in the region of ν₁(HF) and ν_l(HF) vibrations of the OCO⋯HF complex at CO₂ densities increasing from the gaseous to the liquid phase. The evolution of the ν₁(HF) and ν_l(HF) band profiles with increasing system density has been studied. The spectral moments of the two bands and their relative intensities were determined. The spectroscopic data obtained suggest coupling between the large-amplitude librational motions of HF and CO₂ subunits. Excitation of the ν_l(HF) mode may allow the hindered rotational motion of an HF molecule. The spectroscopic result is supported by theoretical analysis. Ab initio calculations at the electron correlation level give a very flat potential-energy surface. The calculated value of the barrier height of the minimum-energy pathway for the complex rearrangement from the linear to the T-shaped structure is 405 cm^–1.