Resonant Raman effect and Fano distortion in the stage-2 graphite donor intercalation compound C/Rb

Raman scattering of the C-C vibration with E2g2 symmetry in stage-2 C/Rb has been studied with different incident photon energies. Resonant enhancement occurs for laser energies in the blue region, close to the threshold for the valence- to conduction-band electronic transition ΩT. The results were fitted with a two-band resonance enhancement model and the fitting procedure yields ΩT=2.6±{}0.15 eV, with a broadening of 0.13 eV. In the red spectral region, the Raman line exhibits a Fano-type distortion, indicating an interaction between the discrete one-phonon excited state, and a continuum which is attributed to electronic excitations.