The intermolecular potential of Ar–HCl: Determination from high-resolution spectroscopy

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Abstract
Two new intermolecular potentials for Ar–HCl are obtained by least‐squares fitting to molecular beam microwave and far‐infrared laser spectra of the Ar–HCl van der Waals complex. In agreement with previous potentials, the equilibrium geometry is found to be linear Ar–H–Cl, with a well depth around 175 cm−1. However, the far‐infrared spectra allow the potential in the region of the linear Ar–Cl–H geometry to be determined as well, and a secondary minimum is found at this geometry, with a depth around 140 cm−1. The secondary minimum arises because the Ar atom can approach closer to the Cl atom at the linear geometry than at a T‐shaped geometry. The fitted potential is used to calculate additional bound states of the Ar–HCl van der Waals complex, which have not yet been observed spectroscopically.