RESONANCE, ANTIRESONANCE, AND DECOHERENCE IN THE EXCITATION OF CHANNELED IONS IN CRYSTALS

We discuss general criteria differentiating incoherent excitation proc esses from coherent processes allowing the production of resonant cohe rent excitation (RCE) of channeled ions in crystals. We give special c onsideration to the ionization of C5+ ions traveling with energies bet ween 15 and 25 MeV along the [100] direction of a gold crystal. We sho w that incoherent ionization of the n=2 state by the valence electrons partially destroys the coherence producing resonant coherent excitati on of the n = 1 --> n = 2 transition by the target static potential. I t thus causes a considerable broadening of the resonance signal, as ob served in the experiments. Finally we show that far from resonance, co herence quenches projectile excitation by the target static potential (anti-Okorokov effect).