EXCITATION-SPECTRA FOR DEGENERATE REARRANGEMENTS

There is already a vast amount of literature on degenerate rearrangeme nts. Graph theory as a tool seems to be used most often with the class ical chemical approach to understand reaction mechanisms, less often w ith the analysis of NMR spectra as influenced by rearrangement process es, and seldom with the analysis of rovibronic spectra and the role of permutation-inversion group. Here we show how the graph-theoretical a pproach can be used to study the rovibronic spectral problem. The grap h-theoretical procedure to estimate the zero-order splitting for rotat ional and vibrational quantum numbers J=K=M=O and upsilon = 0, 1 is el aborated in detail for the internal rotation of ethane and for the Ber ry-pseudorotation of the trigonal bipyramidal skeleton (as for PFS).