Projectile 1s→2p excitation due to electron-electron interaction in collisions of ${\mathrm{O}}^{5+}$ and ${\mathrm{F}}^{6+}$ ions with ${\mathrm{H}}_2$ and He targets

Evidence is presented of an excitation process in ion-atom collisions analogous to electron-impact excitation in free-electron-ion collisions. The production of (1s2s2p${)}^4$P projectile states excited in collisions of (1${\mathrm{s}}^2$2s) ${\mathrm{O}}^{5+}$ and ${\mathrm{F}}^{6+}$ with He and ${\mathrm{H}}_2$ targets was found to increase with projectile energy above ∼0.75 MeV/u, in agreement with an impulse-approximation treatment of 1s→2p electron-impact excitation of ions in collisions with ‘‘quasifree’’ target electrons. Such ion-atom excitations could provide presently unavailable information about inner-shell electron-impact excitation.