Investigation On Interactions Of Fast Ions With Carbon Nanotubes

Interactions of fast ions and molecular ions with carbon nanotubes have been studied theoretically in the present work. The trajectories of protons channeling through single-wall carbon nanotube have been simulated as well as the Coulomb explosion processes of H₂⁺ molecules. In the single proton case, ion trajectory is simulated by solving Newton's equations for ion motion at intermediate energies. The atomic dynamic repulsion is described by a continuum potential based on the Thomas-Fermi-Moliere model, whereas the dynamic polarization of the nanotube electrons is described by a two-dimensional hydrodynamic model, giving rise to the transverse dynamic image force and the longitudinal stopping force. The full statistical analysis of 10³ ion trajectories has been made to demonstrate the actual effect of dynamic polarization on the ion channeling. For H₂⁺ molecule, the basic theory model is the same as that for a single proton, but adding in the interactions of fragment ions, concluding Coulomb forces and wake-like interaction. Then the trajectories of each of the fragment ions can be simulated in order to further study the vicinage effect.It is found that, for the single proton case, in the absence of centrifugal forces, a balance between the image force and the atomic repulsion is found to give rise to ion trajectories which oscillate over peripheral radial regions in the nanotube, provided the ion impact position is not too close to the nanotube wall, the impact angle is sufficient small, and the incident speed is not too high. Otherwise, the ion is found to oscillate between the nanotube walls, passing over a local maxium of the potential in the center of the nanotube. In the case of H₂⁺ molecule, the explosion dynamics is dominated by the bare Coulomb repulsion and it mostly proceeds in the longitudinal direction, accompanied with the radially constrained oscillations of the fragment ions. Strong vicinage effects are found in both the molecule self-energy and stopping power in the early stages of explosions, but they quickly diminish with the increasing dwell time in a manner which depends on the impact molecule speed and its axis orientation.