ON THE INTERSECTION OF POTENTIAL-ENERGY SURFACES IN CHARGE-TRANSFER REACTIONS - A CROSSING SEAM FOR 2 STATES OF THE SAME SYMMETRY IN THE REACTION H++NO(X2-PI)-]H(2S)+NO+(X1-SIGMA+)

An actual crossing seam of two potential energy surfaces of the same symmetry relevant to the charge transfer reaction H++NO(X 2Π)→H(2S)+NO+(X1Σ +) is reported. This crossing seam, R(R)≡[R,r(R),γ(R)] occurs for general Cs geometries. It represents the intersection of the 1,22A′ potential energy surfaces which correlate asymptotically with H(2S) +NO+(X1Σ+) and H++NO(X 2Π), respectively. For R∼2.45-3.65 a0 the seam is exoergic relative to the reactant channel asymptote, H++NO(X 2Π). The present results complement a previous determination of two allowed crossing seams in C∞υ symmetry. Thus these results provide, for the first time, an example of (i) an actual (as opposed to an allowed) crossing seam for a charge transfer reaction and (ii) a system for which both allowed and actual - energetically accessible - conical intersections exist. The actual crossing seam occurs for geometrical configurations in which H+ approaches NO approximately perpendicular to the NO internuclear axis. These configurations are quite distinct from the previously determined allowed crossing seams which correspond to collinear approach. Thus these results are expected to have important implications for the energy redistribution which accompanies charge transfer. The incorporation of this actual crossing seam into any set of potential energy surfaces used to describe the charge transfer process appears essential. It will be quite interesting to see whether this feature is to be found in other charge transfer reactions. © 1992 American Institute of Physics.