Intermolecular van der Waals Vibrations of o-C₆H₄F₂·Ar Complex in the S₁ State

A combined experimental and theoretical study of the intermolecular vibrations of o-C₆H₄F₂·Ar van der Waals complex is reported. The three bands of intermolecular van der Waals vibrations, Which are from the electronic trasnition （S₁←S₀）are exhibital. Using resonant two-photon ioization spectrometry,together with time-of-flight mass spectrometry, in supersonic molecular beam. For complex o-C₆H₄F₂·Ar, van der Waals vibration levels are calculated by the quantUm method of linear-combination of three-dimensional harmonic oscillator products and Lennard-Jones potential, which is very close to the experimental spectrum, The vibration of atom Ar in o-C₆H₄F₂·Ar compare with that in p-C₆H₄F₂·Ar, which the vibrational force constant along the direction perpendicular to the ring plane is indepent on the relative position of two atoms F in-ring plane, but the two vibrational force constants,along the direction parallel to the ring plane, are related to closely the position of two atoms F in the ring plane.