Bond types of molecular orbitals and the photoelectron spectrum

The vibrational structures of the photoelectron spectra for diatomic molecu les can be accounted for in terms of the slope of the orbital energy curve in the conventional correlation diagram with respect to internuclear distan ce. The vibrational structures of the photoelectron spectra for simple poly atomic molecules HCN, C2H2, and AH(2) type of hydrides can also be accounte d for in terms of the slopes of the orbital energy curves in the correlatio n diagrams with respect to angles, as well as distances. Among all correlat ion diagrams, the slopes in the distance correlation diagram are related to the criterion for bond type-the positive for "bonding," the negative for " antibonding," while slopes with small magnitudes for "nonbonding." The Fock matrix elements within the bond orbital basis provide heuristic and system atic rationalization of the slopes for the orbital energy curves. (C) 2001 John Wiley & Sons, Inc.