A molecular orbital approach to the fragmentation of the acetaldehyde cation radical

The microscopic process of the -cleavage of the acetaldehyde cation radical is treated by means of the molecular orbital method. Two kinds of transition state for two different dissociation channels are located on the multidimensional potential surface. Supposing the Franck-Condon principle in the ionization process, the importance of the non-equilibrium initial state where two specific modes are excited is emphasized. In order to clarify the mechanism of these fragmentation processes a simple model of the intra-molecular energy transfer is constructed considering the anharmonicity of the potential energy function.