A THEORETICAL-STUDY OF CHARGE-TRANSFER REACTIONS - POTENTIAL SURFACE AND CLASSICAL TRAJECTORY STUDY N+CO-]N+CO+

Potential energy surfaces (PESs) of the charge-transfer reaction N+ + CO --> N + CO+ have been calculated by ab-initio MO methods in order to shed light on the detailed reaction mechanism. This reaction is a mode-specific one in which the vibrational modes of the product CO+ cation are populated in a non-Boltzmann distribution. The ab-initio MO calculation including electron correlation gives a strongly bound [NCO+] complex (1(3) Sigma(-)) on the ground-state PES and a weakly bound [NCO+]* complex (2(3)A '') on the first excited-state PES. On the basis of the ab-initio MO calculations, we propose a reaction model composed of dual reaction channels in the charge-transfer process: one is an intermediate channel model in which the reaction proceeds via an intermediate complex (the ground-state NCO+ complex), and the other is a direct channel model in which the reaction proceeds directly without the ground-state intermediate. The mechanism of the charge transfer is discussed based on the PES characteristics. Furthermore, using LEPS (London-Eyring-Polanyi-Sato)-PESs fitted to the ab-initio PESs, classical trajectory calculations were performed. We find that the intermediate channel gives vibrationally excited CO+ cations, whereas the CO+ cation formed via the direct channel is in the vibrational ground state.