Direct imaging of excited electronic states using diffraction techniques: theoretical considerations

We illustrate that the charge in electron density distribution upon electronic excitation of atoms can significantly change their X-ray and electron diffraction, suggesting that electronic structures of excited electronic states may be directly observed using optical pump-diffraction probe techniques. Three electronic states of lithium are used to demonstrate changes in X-ray and electron diffraction patterns. Even though the changes in the total electron densities are small, significant changes are observed in inverse k space, the domain of diffraction experiments. The pump-probe diffraction patterns are interpreted in terms of extended and non-spherical structures of excited electronic states.