Nuclear Motion of Core ExcitedBF3Probed by High Resolution Resonant Auger Spectroscopy

High resolution resonant Auger spectroscopy applied to the core excitation of ${\mathrm{BF}}_3$ reveals that the kinetic energy of the spectator Auger electrons stays constant when the photon energy is scanned through the B $1s\to {2a}_2^{\prime \prime }$ resonance, whereas the kinetic energy of participator Auger electrons shows a linear photon energy dependence. These nondispersive and dispersive effects are theoretically reproduced using a quasi-Jahn-Teller model and by treating the Auger emission process as a coherent second-order quantum process.