Resonant Inelastic X-Ray Scattering in Hexagonal Boron Nitride Observed by Soft-X-Ray Fluorescence Spectroscopy

Photon-excited B K fluorescence spectra were measured for hexagonal boron nitride using tunable synchrotron radiation below and above the B K edge. We report Raman-like resonant inelastic scattering of soft x rays involving excitation of delocalized valence-band electrons. The inelastic scattering features track with the excitation energy below threshold, go through a resonance as the excitation is tuned to the B(1s) core-exciton energy, and evolve into incoherent fluorescence as the excitation is raised further. The energy loss is identified as equivalent to an electronic transition of valence $\sigma$ electrons to ${\pi }^{*}$ conduction-band states.