Interaction of low energy reactive ions with surfaces. III: Scattering of 30-200 eV Ne+, O+, C+ and CO+ from Ni(111)

• Published in: The Journal of chemical physics 1988-05, Vol.88 (9), p.5902-5913
• Main Authors: KASI, S. R, KILBURN, M. A, KANG, H, RABALAIS, J. W
• Format: Article
• Language: English
• Subjects: Atomic and molecular collision processes and interactions; Atomic and molecular physics; Exact sciences and technology; Other topics in atomic and molecular collision processes and interactions; Physics
• ISSN: 0021-9606; 1089-7690
• DOI: 10.1063/1.454523

Time-of-flight (TOF) and energy distributions of 30–200 eV Ne+, O+, C+, and CO+ scattered from Ni(111) have been investigated using pulsed ion beam techniques and classical trajectory simulations. The experiments probe the interaction potentials and the applicability of the binary collision approximation in the low energy range. The experimental scattering energies are in good agreement with the energies predicted by the classical treatment. Scattering of atomic projectiles at primary energies as low as 30 eV (scattered energies ∼15 eV) has been detected and is characterized by sharp scattering peaks. The lower limit of detectability is determined by the sensitivity of the detector to slow neutrals. The reactive ions are completely neutralized in the scattering collision while some of the Ne+ ions survive single scattering events. Scattering of molecular CO+ produces a broad scattered flux distribution due to partial dissociation and scattering of both molecular and atomic species. Trajectory simulations have been performed using a purely repulsive Biersack–Ziegler potential and a Biersack–Ziegler potential combined with a Morse potential to include an attractive component. The importance of the attractive potential in describing the trajectories of the reactive ions increases with decreasing ion energy. This attractive potential is shown to be responsible for preferential neutralization of reactive ions by altering the trajectories so that the distance of closest approach is shorter and the time spent near the surface is longer, thus enhancing electronic interaction between colliding species. Energy level diagrams are used to discuss the neutralization transitions and the differences between the reactive and noble ions.