Observation and rovibrational analysis of the intermolecular HCl libration band v41 in OC-HCl.: Modeling of the intermolecular potential energy surface

The high-resolution far-infrared spectrum of the intermolecular HC1 libration band v(4)(1) of the OC-H(35)C1 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-HC1 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 nu(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.