Energy and Charge Transfer of Hyperthermal-Energy Heavy Ions Scattering on Target Surfaces with Low Atomic Mass

Doctoral Dissertation

Abstract

Limited information is available on the scattering dynamics of heavy projectiles from a surface composed of light atoms, especially in the hyperthermal energy regime, in spite of increased importance from both theoretical and practical perspectives. The scattering of hyperthermal Br+ ions on highly oriented pyrolytic graphite (HOPG) serves as a desired model system to investigate detailed energy and charge transfer processes during a violent collision. The angle-resolved velocity distributions of the scattered ions are measured under a wide set of incident conditions. The variation of the distributions with initial kinetic energy reveals unexpected and complicated scattering dynamics which can not be properly described by simple models such as parallel momentum conservation or binary collision models. Instead, it is attributed to successive many-body collisions between the projectile and a dynamically corrugated surface induced by the energetic impact. Br+ ions are efficiently converted to neutral atoms or Br– upon collision with HOPG. The anion yield calculated by integrating the probability density of scattered ions over all exit angles and velocities exhibits a strong resonance at ~30-eV incident energy. For incident energies less than 30 eV, the anion yield is positively correlated to the final exit velocity, in agreement with conventional charge transfer theories applied to light projectiles scattering on a static surface. The steep drop of the anion yield at high incident energy is attributed to surface penetration and trapping of the incident projectile.

The scattering of Cl+ on HOPG as well as Ni(111) supported monolayer graphite surface under analogous incident conditions provides a unique opportunity to examine the effect of mass and physical properties of the surface on the scattering dynamics. The results indicate that for the heavy projectile/light surface atom combination the interaction between surface atoms plays a key role in the energy transfer process.

Attributes

Attribute NameValues
URN
  • etd-04162012-170434

Author Li Zeng
Advisor J. Daniel Gezelter
Contributor Brian M. Baker, Committee Member
Contributor Gregory V. Hartland, Committee Member
Contributor J. Daniel Gezelter, Committee Member
Contributor Dennis C. Jacobs, Committee Member
Contributor S. Alex Kandel, Committee Member
Degree Level Doctoral Dissertation
Degree Discipline Chemistry and Biochemistry
Degree Name PhD
Defense Date
  • 2012-04-12

Submission Date 2012-04-16
Country
  • United States of America

Subject
  • dynamic surface corrugation

  • polar velocity map

  • AES

  • LEED

Publisher
  • University of Notre Dame

Language
  • English

Record Visibility Public
Content License
  • All rights reserved

Departments and Units

Files

Please Note: You may encounter a delay before a download begins. Large or infrequently accessed files can take several minutes to retrieve from our archival storage system.