Trajectory Effects on the Negative Charge-State Fraction of Deuterium Reflected from a Sodium Target

Measurements of the negative charge-state fraction of the reflected particles resulting from D2+ bombardment of a thick Na target are presented. Incident energies of 6 keV and 12 keV produced particles with exit energies between 400 eV and 5000 eV. The incident angle was 0° from the surface normal and the exit angle was 85°, giving a scattering angle of 95°. The negative charge-state fraction was 0.20 at an exit energy of 400 eV and decreased monotonically to 0.05 at an exit energy of 5000 eV. The negative charge-state fraction was also independent of the incident energy. The present results are compared to measurements made at an incident angle of 85° with the same exit angle as above, where there is a remarkable difference in the negative charge-state fractions. The differences in the results for the different incident angles are discussed in terms of a trajectory-dependent formation probability of the negative ions.