De-excitations
If the electronic ground state of a molecule has double-excitation character and the excited state only single-excitation character, then you can view the molecule as being "de-excited." Electrons are taken from a higher lying orbital and moved into a lower lying orbital. A recent paper tries to formalise this idea by computing an expectation value of the particle-hole permutation operator. We take the two-body exciton wavefunction, switch the electron and hole and see how much it resembles the original wavefunction. Читать дальше...