Crystal-momentum-resolved electronic structure of solids using resonant soft-X-ray fluorescence spectroscopy

Resonant inelastic X-ray scattering (RIXS) has been observed in graphite an d hexagonal boron nitride (hBN) above and below their K edges. Below the co re threshold, inelastic-loss features are observed, which disperse linearly with excitation energy, but as the excitation goes above the core binding energy, nonlinear dispersive effects are observed in graphite but not in hB N. We show that these two effects, which have previously been thought of as separate processes, i.e. resonant X-ray Raman scattering (below threshold) and RMS (above threshold), are in fact described by the same physics of co herent fluorescence. Very good agreement between experiment and simulated R IXS is achieved using a simple one-electron framework. The role core-excito ns play in the RIXS process is examined in finer detail, by using narrow-ba nd excitation. Our results indicate that core-hole effects play a minor rol e in the RIXS observed from graphite but are more pronounced in hBN. (C) 20 00 Elsevier Science B.V. All rights reserved.