Electron capture into excited projectile states in collisions of 100 keV Ne^z+ (z=1,2,3,4) with He, H₂ and Ar

By means of absolute light intensity measurements between 2000 and 6500 AA cross sections have been determined for electron capture into excited projectile states during collisions between 100 keV Ne^z+ (z=1,2,3,4) and different target gases. Total single-electron-capture cross sections have been obtained by measuring ion-current attenuation. There is direct experimental evidence that capture into excited states is related to the energy defect of the respective reaction and furthermore, that for higher projectile charge states an important part of the single-electron-capture process is caused by capture into excited states with moderate exothermic energy defects.