Valence states of carbon in π-electron systems: II. Excited states and ions† Supported in part by the United States Atomic Energy Commission under contract with the Union Carbide Corporation and in part by the National Science Foundation

Changes in atomic orbitals (AO) brought about by changes in molecular wavefunctions are studied by minimizing the energy of carbon in atomic valence states appropriate for ions and excited states of alternant hydrocarbons. It is found that positive-ion and triplet-state 2pπ AO's are more contracted than in alternant hydrocarbon ground states. Negative-ion and excited-singlet 2pπ AO's are more expanded than in the ground states. These AO changes may be negligible for large molecules but are increasingly important for molecules smaller than naphthalene.