Study of the Potential Surfaces of the Ground and First Excited Singlet States of H2O

Abstract

The lowest ¹A′ and ¹B₁ potential surfaces of the water molecule are calculated and are discussed together with the results of previous investigations concerning the reactions of O(¹D) and O(³P) with ${\mathrm{H}}_2{(}^1{\Sigma }_g^{+}\mathrm{).}$ It is found that the insertion of O(¹D) into an H₂ molecule to yield H₂O and the abstraction of hydrogen to yield OH and H both occur preferentially for an acute angle approach of the oxygen atom with respect to the H–H bond. The activation energy of abstraction is found to be small enough to account for the formation of OH radicals which are also found as products during O(¹D) insertion reactions. It is illustrated that the symmetry rules based on second‐order perturbation theory may serve as a useful guide in the initial mapping of a potential energy surface. Finally, the electronic charge and spin density distributions of the lowest ¹B₁, ³B₁, and ¹A₁ states are compared and discussed.