On-top conditional correlation functions of many-electron theory are rearranged into a set of correlon quasiparticles representing the local effect of electron correlation in the ground and excited states. An individual correlon is characterized with a one-particle wave function, the imaginary part of which (or covalent correlon) gives the amplitude of the on-top depletion of the (conditional electron) charge (ODC) due to (strong) electron correlation. In its turn, the real part (ionic correlon) gives the amplitude of the on-top accumulation of the (electron) charge (OAC) due to the ionic squeezing of electrons. The proposed correlon theory is applied to analyze the local correlation effects in the ground and first excited states of the hydrogen molecule as well as of the equidistant and alternate linear hydrogen chains from ${\mathrm{H}}_4$ to ${\mathrm{H}}_{12}$. The covalent and ionic correlons obtained at the multiconfigurational self-consistent-field level of correlated functions are demonstrated to be the robust descriptors of the covalency of the ground and the ionicity of the excited ${\mathrm{H}}_n$ states.

• Received 4 September 2020
• Accepted 6 November 2020

DOI:https://doi.org/10.1103/PhysRevA.102.052829