EXTENDING THE COLLOCATION METHOD TO MULTIDIMENSIONAL MOLECULAR-DYNAMICS - DIRECT DETERMINATION OF THE INTERMOLECULAR POTENTIAL OF AR-H2O FROM TUNABLE FAR-INFRARED LASER SPECTROSCOPY

We present an extension of the collocation method developed by Peet and Yang (J. Chem. Phys. 1989, 91, 6598) for calculating the bound states of rotating atom-diatom systems to atom-polyatom complexes. The method is shown to be general, accurate, efficient, and straightforward to implement. The collocation algorithm is incorporated into a nonlinear least-squares program, which is used in a direct fit of far-infrared vibration-rotation spectra of the Ar-H2O complex to a detailed analytical model for the anisotropic intermolecular potential energy surface. The surface denoted AW1 was obtained without any dynamical approximations. The minimum (De = 174.7 cm-1, Re = 3.598 Å) in the intermolecular potential surface occurs for the argon located in the plane of the H2O, nearly perpendicular to the symmetry axis. © 1990 American Chemical Society.