POTENTIAL-ENERGY SURFACES OF CARBON-DIOXIDE

Several bent valence states of CO2 are characterized by means of full- valence-space MCSCF calculations. The ground state potential energy su rface exhibits a double well corresponding to a ring minimum, with C(2 v)symmetry ((1)A(1)) and a 73.1 degrees OCO angle, in addition to the linear ((1) Sigma(g)(+)) global minimum. The transition state for the ring opening process, which has a barrier of 12.1 kcal/mole with respe ct to the ring minimum, is however found to have C-s symmetry. Double minima are also shown to exist for the (1)A(2), B-1(1) and B-1(2) exci ted states. However, in these cases all minima are bent. Cross section s through the ground state potential energy surface corresponding to t he two collinear exchange reactions O(D-1) + CO((1) Sigma(+)) --> OC(( 1) Sigma(+)) + O(D-1) C(P-3) + O-2((3) Sigma(g)(-)) --> CO((1) Sigma()) + O(D-1) are also calculated and their energy contour maps are repo rted. The latter reveals the existence of a stable linear intermediate with the structure COO. (C) 1994 John Wiley and Sons, Inc.