Orbital stress and transition stress of diatomic molecules

Abstract

The orbital stress, which is the force of the electrons in a given molecular orbital opposing the repulsive stress (tension) between the nuclei, has been calculated for some diatomic molecules (N2, N+2, C2, O2, O+2, CO, CO+, NO, NO+, CF). The transition stress is defined as the difference between the orbital stress of an upper molecular orbital and that of a lower molecular orbital involved in an electronic transition. It is shown that the transition stress is a fundamental property of molecules. The bond lengths of various excited states are related to the transition stress and the bond length of the ground state. The rotational constants of excited states are linear functions of the transition stress, provided configuration interaction between the excited states is not very strong. The complexity of the vibrational structure in photoelectron spectra is related to the orbital stress. The theoretical results are in good agreement with experimental data. An analysis in terms of the orbital stress and the transition stress for polyatomic molecules may serve to predict the chemical relaxation paths that follow excitation of a core electron in a molecule and subsequent Auger decay.