Observation and Rovibrational Analysis of the Intermolecular HCl Libration Band v_4~1 in OC-HCl. Modeling of the Intermolecular Potential Energy Surface

摘要

The high-resolution far-infrared spectrum of the intermolecular HCl libration band v_4~1 of the OC-H~(35)Cl heterodimer is recorded in the gas phase by means of Fourier transform IR spectroscopy in a static multipass absorption cell at 137 K using a synchrotron radiation source. This is the first direct observation of an intermolecular vibration band of the OC-HCl dimer in the gas phase. The rotational structure of the band has the typical appearance of a perpendicular band of a linear polyatomic molecule. The structure is analyzed to yield the band origin v_0 = 201.20464(27) cm~(-1) together with values for the upper state rotational constant, the upper state quartic and sextic centrifugal distortion constants, and the l-type doubling constant. The determined values for the rotational constant and the centrifugal distortion constants are used to obtain a Morse potential for the stretching of the intermolecular distance. The results are compared to the results from quantum-chemical calculations.