Bader-Pearson-Salem approach

Bachler [36], has shown how to accomplish the first step in his extension and amplification of the Bader-Pearson-Salem approach (See footnote 15 in Chapter 1), according to which the symmetry properties of vibrational modes activated in an electronically excited state are determined by the irreps of the orbitals between which the transition takes place. The way is open to following with the second step. 

Bachler has applied his extension of the Bader-Pearson-Salem approach [36] to both isomerization processes. His preliminary results indicate that vibrational modes that would be expected to contribute to the reaction coordinates for isomerization to benzvalene are indeed excited in Si and those leading to Dewar benzene are excited in S2 [41]. 

One approach of this type is due originally to Bader, who used perturbation theory to show that unimolecular reaction is particularly favoured along a normal co-ordinate whose symmetry is the same as that of the transition density between the ground state and a low-lying excited state, because then second-order Jahn-Teller interaction depresses the energy of the ground state. The idea has been taken up by Salem and Pearson and used, in conjunction with a semilocalized MO model, to determine the allowed routes in the pyrolysis of cyclobutane and cyclohexene. Fukui et a/. have described a similar method. 

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See also in sourсe #XX -- [ , , ]

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