A STUDY OF THE ARCL2 VAN-DER-WAALS COMPLEX - AB INITIO-BASED POTENTIAL-ENERGY SURFACES, THE RELATIVE STABILITY OF CONFORMERS, AND THE HIDDEN MICROWAVE-SPECTRUM

Two new ground state potential energy surfaces have been obtained for the ArCl2 Van der Waals complex, one purely nb initio, rite other cons tructed from empirical ArCl potentials modified in terms of ab initio data for the ArCl2 and ArCl moities, The ab initio surface has a well for the linear conformer that is slightly deeper than that for the T-s haped conformer, but inclusion of the zero-point energies reverses the relative binding in the two configurations. The microwave spectrum ha s been calculated using the new potential surfaces, and a series of Li nes that can be:associated with the linear conformer have been predict ed. Possible reasons for their nonobservability under the usual experi mental conditions are discussed. A simple modification which employs e mpirical information on the ArCl potentials used in modelling the ArCl 2 potential surface transforms the well for the T-shaped conformer int o the global minimum, with a dissociation energy that lies within 0.5% of the experimental value, and microwave transition energies that dev iate from experimental values by no more than 1.3%. A final two-parame ter scaling allows reproduction of both the experimental D-0 value (wi thin experimental uncertainty) and the positions of all observed micro wave lines (within 0.02%) for each of the ab initio and empirically ba sed potential surfaces. (C) 1997 American Institute of Physics.