Probing symmetry breaking upon core excitation with resonant x-ray fluorescence

Resonantly excited x-ray fluorescence spectra of the benzene molecule are presented and analyzed in terms of symmetry-selective resonant scattering processes. The sharp frequency dependency that is observed can be understood from strict parity and symmetry-selection rules operating in the full ${\mathit{D}}_{6\mathit{h}}$ point group symmetry. The experimental results prove that the electronic symmetry is not broken for the lowest unoccupied level involved in the resonant x-ray emission process.