A theoretical treatment of the intersystem crossing in the spin-forbidden reaction NO(X2Π)+CO(X1Σ+)→N(4S)+CO2(X1Σg+)

The mechanism of the spin-forbidden reaction NO(X(2)Pi) + CO(X (1)Sigma(+)) --> N(S-4) + CO2(X (1)Sigma(g)(+)) is considered. Two minimum energy points on the doublet-quartet crossing surface are reported using multireference configuration interaction (MRCI) wavefunctions. The lowest-energy crossing point has an approximate C-2v structure resembling the products N + CO2. This region lies 60 kcal/mol above the reactant channel, suggesting that the title reaction would not occur under typical combustion conditions. A higher-energy point with a linear structure is also located. Two local minima on the lowest (2)A " potential energy surface are reported at the QCISD and MRCI levels. (C) 1999 Elsevier Science B.V. All rights reserved.