The anisotropic intermolecular potential energy surface of argon - hydrogen-chloride from intracavity far infrared laser/microwave double resonance spectroscopy.

摘要

Three intermolecular vibrational transitions have been measured in the Ar-HCl van der Waals complex using a sensitive new high resolution far infrared laser spectroscopy technique. The molecular constants determined from the spectra provide a characterization of the anisotropic intermolecular potential energy surface which is both qualitatively and quantitatively superior to those extracted from other experiments.; The apparatus incorporates a supersonic free jet expansion source inside the optical cavity of a far infrared laser and employs the Stark effect for tunability. Microwave/far infrared double resonance capabilities have provided a definitive method of identifying the quantum states involved in an otherwise complex field-tuned spectrum.; Hyperfine-resolved vibration-rotation spectra for both chlorine 35 and 37 isotopic species of Ar-HCl have been measured for the lowest {dollar}Sigma{dollar} bending vibration, the lowest {dollar}Pi{dollar} bending vibration and the lowest stretching vibration. From the spectra combinations of the values of the band origin, rotational constant, centrifugal distortion constant, dipole moment, {dollar}ell{dollar}-type doubling constant and chlorine nuclear quadrupole coupling constants have been determined for each of the six bands. These results have revealed new features of the intermolecular potential energy surface, particularly the existence of a local minimum at the linear Ar-ClH configuration, in addition to the global minimum at the linear Ar-HCl geometry.