Global potential energy surfaces of the lowest two (sup 1)A(prime) states of the ozone molecule: Theoretical determination and analysis

摘要

The two lowest 1A(prime)potential energy surfaces of the ozone molecule are determined and analyzed using accurate ab-initio MCSCF calculations. The shape-scale perimetric coordinates for triatomic molecules are discussed and further developed. Because the previously determined intersection between these two surfaces of like symmetry is unusual, much of the present work involves this intersection. The relevant theory of intersections is reviewed, and a method for characterizing intersections according to the topology of the surfaces in their vicinity is developed. The reasons for this particular crossing in ozone are investigated. The intersection point in C(sub 2v) symmetry is part of a larger, 1-dimensional intersection seam in C(sub s) symmetry. This seam is shown to consist of four branches. A new method for determining an intersection point in a two-dimensional coordinate space, based on the wavefunction phase-change theorem of Herzberg-Longuet-Higgins, is also developed. Finally, global mappings of the two potential energy surfaces in the scale-shape perimetric coordinates are determined. The minima of the two surfaces, their dissociation and rearrangement paths, and the map of the energy difference between them are all discussed. It is shown that direct formation of the ring structure of ozone from O(sub 2) and O is improbable, and that there is no rearrangement pathway on the ground state representing the interchange of two atoms.