Quantum Mechanics of Mobile Electrons in Conjugated Bond Systems. V. Empirical Determination of Integrals between Carbon Atomic Orbitals from Experimental Data on Benzene

It is shown that the experimental information given in the ultraviolet spectrum of benzene uniquely determines the two-center Coulomb integrals between the 2pπ atomic orbitals of carbon as a function of the internuclear distance. The calculations are carried out including all terms involving neighbor overlap. For the many-center electron-interaction integrals, the Mulliken approximation and the London approximation are both considered with little difference in the results. Some peculiar properties of the empirically determined distance dependence are compared with the theoretical behavior of two-center Coulomb integrals. The empirical values for the resonance integral and the Coulomb integral are also found. The investigation differs from similar work of Pariser by the inclusion of overlap effects.