Far-infrared vibration-rotation-tunnelling spectroscopy of ArDCl: A critical test of the H6(4, 3, 0) potential surface

Three intermolecular vibrations of the ArDCl complex have been observed by tunable far-infrared laser spectroscopy in a supersonic planar jet. Vibration-rotation-tunnelling transitions to states correlating to the j = 1, Θ = 0, the j = 2, Θ = 0, and the j = 2, Θ = 1 internal rotor levels of DCl have been measured for both chlorine isotopes with nuclear quadrupole hyperfine resolution. The fitted spectroscopic constants are compared with recent calculations from the new H6(4, 3, 0) ArHCl potential by Hutson and it is concluded that, although the new potential is very accurate, significant discrepancies between observed and calculated values exist for states which probe the secondary minimum (ArClH) of the potential