Visible and UV Luminescence in Ion Beam‐Neutral Collisions

Ions extracted from a plasma source are magnetically mass analyzed and traverse a gas filled scattering chamber. Optical emission from collisionally excited species is observed with 10 Å resolution and photon counting, signal averaging techniques. The projectile ions Ar + , Ne + , C + , N + , O + were used in combination with He, Ne, Ar, NO, CO, N 2 and O 2 as targets. The processes observed include a) target excitation (example: N + + NON + + NO*), b) chemiluminescence (e.g. N + + NON + 2 * + O), c) charge exchange resulting in a radiating state (e.g. Ne + +CONe + CO + * ), d) dissociative charge exchange leading to excited products (e.g. Ne + + CONe + C + * + O). Preliminary results are presented on the spectral distribution and excitation functions of various emissions. In addition to the chemiluminescent ion‐molecule reaction N + + NON +* 2 + O, its isoelectronic neutral counterpart C + NOCN* + O was also observed, the fast C atoms being produced in a preceding charge exchange step. The violet bands of reactively formed CN appear to indicate an inversion of the vibrational level population. The comet tail bands of CO + , resulting from charge transfer with Ar + and Ne + disagree distinctly with Franck‐Condon predictions, but independent of ion kinetic energy between 20 and 1000 eV. By contrast, the N* 2 first negative system from Ar + , Ne + /N 2 collisions shows strongly energy dependent deviations from the Franck‐Condon principle.