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

Photon-excited B {ital K} fluorescence spectra were measured for hexagonal boron nitride using tunable synchrotron radiation below and above the B {ital 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(1{ital s}) 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}{sup *} conduction-band states. {copyright} {ital 1996 The American Physical Society.}