Photoelectron spectroscopy, valence bond description

Variable Energy Valence Photoelectron Spectroscopy—Inverted Bonding Description 696... 

Thus the spectrum which arises when Eq. (8) is Fourier transformed consists of a set of -functions at the energies corresponding to the stationary states of the ion (which via the theorem of Koopmans) are the one-electron eigenvalues of the Hartree-Fock equations). The valence bond description of photoelectron spectroscopy provides a novel perspective of the origin of the canonical molecular orbitals of a molecule. Tlie CMOs are seen to arise as a linear combination of LMOs (which can be considered as imcorrelated VB pairs) and coefficients in this combination are the probability amplitudes for a hole to be found in the various LMOs of the molecule. 

The chemistry of carbon monoxide is, however, more often rationalised on a qualitative molecular orbital (MO) basis rather than in terms of its valence bond description. Figure 2.1 depicts the energy level MO diagram for carbon monoxide with occupied orbital energies determined by photoelectron spectroscopy. An approximate correlation can be made between valence bond and MO descriptions through assignment of the filled orbitals 4o and 5o to lone pairs on oxygen and carbon respectively and orbitals 3a and... 

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