We discuss general criteria differentiating incoherent excitation processes from coherent processes allowing the production of resonant coherent excitation (RCE) of channeled ions in crystals. We give special consideration to the ionization of C${}^{5+}$ ions traveling with energies between 15 and 25 MeV along the $〈100〉$ direction of a gold crystal. We show that incoherent ionization of the $n=2$ state by the valence electrons partially destroys the coherence producing resonant coherent excitation of the $n=\stackrel{\ensuremath{\rightarrow}}{1}n=2$ transition by the target static potential. It thus causes a considerable broadening of the resonance signal, as observed in the experiments. Finally we show that far from resonance, coherence quenches projectile excitation by the target static potential (anti-Okorokov effect).