ABSTRACT
In the intervals defined by two consecutive eigenvalues of S there are alternately two or no dgenvalnes of T . Eq.(67) represents a novel interlacing theorem which is not restricted merely to the dgenvalne spectra of such gnq»hs. Because for completely conjugated unsaturated systenos the eigenvalues X f and Aj may be identified with t-MO energies, the interlacing should be substantiated by photoelectron spectra; this is verified by numerous examples. For more details the reader may wish to consult the papers cited at the end of this chapter.
