The Auger-Doppler effect in the experimental spectra of HF and DF is presented. and the dynamics of ultra-fast dissociation in the core-excited state are discussed. The Doppler splitting of the atomic Auger peak is calculated and simulated using a classical model and a very good agreement is found between experiment and simulation. It is shown that the difference in photon energy relative to the resonance is transferred completely into the kinetic energy release (KER). This is expected to be a general phenomenon, but is clearly illuminated in the HF/DF case, Thus the fragment velocity can be controlled through photon energy detuning. (C) 2002 Elsevier Science B.V. All rights reserved.