Problems Associated with Close-Lying Electronic States

However, molecular distortion to lower symmetry can be real and, in fact, occurs quite frequently in radical ions and diradicals, as discussed in the section on problems associated with close-lying electronic states. Even in the case of allyl, where higher level calculations and experiments both show that molecular distortion of the C2. equilibrium geometry to Q is an artifact of ROHE calculations, antisymmetric distortion of the C—C bonds will invariably occur for sufficiently long C—C bond lengths. It is obviously more favorable to dissociate allyl radical into a vinyl radical plus methylene than into two methylenes and a CH radical. 

PROBLEMS ASSOCIATED WITH CLOSE-LYING ELECTRONIC STATES... 

Problems Associated with Close-Lying Electronic States 45... 

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