Time-dependent electron localization function
  In this article we present a generalization of the electron localization function (ELF) that can be used to analyze time-dependent processes. The time-dependent ELF allows the time-resolved observation of the formation, the modulation, and the breaking of chemical bonds, and can thus provide a visual understanding of complex reactions involving the dynamics of excited electrons. We illustrate the usefulness of the time-dependent ELF by two examples: the pi-pi* transition induced by a laser field, and the destruction of bonds and formation of lone pairs in a scattering process. 
Tobias Burnus, Miguel A.L. Marques, and Eberhard K.U. Gross