High resolution resonant Auger spectroscopy applied to the core excitation of BF{sub 3} reveals that the kinetic energy of the spectator Auger electrons stays constant when the photon energy is scanned through the B 1s{r_arrow}2a{sup {prime}{prime}}{sub 2} 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. {copyright} {ital 1997} {ital The American Physical Society}