Resonant elastic x-ray scattering of graphite and diamond at the carbon K threshold

Resonant elastic x-ray scattering (REXS) was observed at the carbon K thres hold of graphite powder, and a small amount of excitonic x-ray scattering w as observed in diamond. A comparison of the energy spectra of REXS in graph ite with the carbon K x-ray absorption spectra, and with the calculated ene rgy spectra of the unoccupied density of states, suggests that REXS is caus ed by the transition of the ''participator'' electrons via p pi* states in sp(2)-carbon atoms. The probabilities of transition to "participator" REXS or to "spectator" resonant inelastic x-ray scattering in the resonant radia tive-decay process of graphite powder, were determined from REXS spectrosco py to be approximately 47% and 53%, respectively.