AB-INITIO BASED POTENTIAL-ENERGY SURFACES, MICROWAVE-SPECTRUM, AND SCATTERING CROSS-SECTION OF THE GROUND-STATE NE-CL-2 SYSTEM

The high-level ab initio potential energy surface (PES) for NeCl2 in t he ground electronic State predicts the energy minimum in the linear g eometry (L-well) to be slightly deeper than that in the T-shaped geome try (T-well). The experimental D-0 and R-0 values are reproduced withi n uncertainties of measurements by both adding the calculated perturba tion of the Ne-Cl interactions due to intramolecular forces in Cl-2 to empirical NeCl potentials, and by Linearly extrapolating or simply sc aling the ab initio PES. These procedures lead to equal or even revers ed relative depths of the two wells, in accord with both predictions o f an atom-atom model using equivalently accurate ab initio NeCl potent ials and variation of the ab initio PES with increasing accuracy of ca lculations. The D-0 value for the L-well is predicted to be less than that for the T-well by 2.4 to 5.2 cm(-1) for different scaling schemes . The calculated lowest energy rovibrational states associated with ea ch of two conformers show negligible mutual influence, while the effec t of the L-well on,the rovibrational wave functions for the next vibra tional states associated with the T-well is found to be rather importa nt. Microwave spectra are predicted for each PES obtained, and include portions originating from the L-well. The calculated scattering Cross section reproduces well the experimental data and is found to be sign ificantly contributed by the L-well. (C) 1998 American Institute of Ph ysics.