Resonant elastic x-ray scattering of graphite and diamond at the carbonKthreshold

Abstract

Resonant elastic x-ray scattering (REXS) was observed at the carbon K threshold of graphite powder, and a small amount of excitonic x-ray scattering was observed in diamond. A comparison of the energy spectra of REXS in graphite with the carbon K x-ray absorption spectra, and with the calculated energy spectra of the unoccupied density of states, suggests that REXS is caused by the transition of the ``participator'' electrons via $p{\ensuremath{\pi}}^{*}$ states in ${\mathrm{sp}}^{2}$-carbon atoms. The probabilities of transition to ``participator'' REXS or to ``spectator'' resonant inelastic x-ray scattering in the resonant radiative-decay process of graphite powder, were determined from REXS spectroscopy to be approximately 47% and 53%, respectively.