Real-space description of molecular processes in electronic excited states

This chapter reviews several applications of quantum chemical topology to the study of molecular processes in electronic excited states. The charge redistribution that occurs as a consequence of an electronic transitions is analyzed in terms of the electron density and its multipole moments; the energy transfer involved in the process is accounted for in terms of the interacting quantum atoms (IQA) method. The examples include the excitation of simple molecules, excimer formation, excited-state intramolecular proton transfer, and photodissociation processes, in some cases involve avoided crossings or conical intersections of electronic states. In addition, the implementation of the IQA method for the MRCI, CASPT2, and EOM-CCSD electronic structure methods is briefly described.