This thesis studies the non-linear (Barkas) effects on stopping of fast moving molecular ions through solids. We model the solid target by a rigid lattice of positive ion cores surrounded by a gas of electrons. To model the electron gas we use a hydrodynamic model with a Thomas-Fermi-von Weizsacker expression for the internal energy. The disturbance to the charge density and velocity profile of the gas due to the intruder is assumed small and a perturbation expansion is used. The gas is assumed to be initially at rest. A derivation for the first and second order stopping force on an projectile due to the induced charge density of the target is given. Structure factors are introduced to capture the physics relating to the structure of the projectile and to allow maximum flexibility and generalization. The second order stopping force is calculated using a novel ”holepunch” integration method and is compared to other available methods. Results are obtained for the case of a dicluster of protons which are colinear with their direction of motion as well as for a dicluster of protons which are randomly oriented incident on an aluminum target and compared to the single proton case.

This thesis studies the non-linear (Barkas) effects on stopping of fast moving molecular ions through solids. We model the solid target by a rigid lattice of positive ion cores surrounded by a gas of electrons. To model the electron gas we use a hydrodynamic model with a Thomas-Fermi-von Weizsacker expression for the internal energy. The disturbance to the charge density and velocity profile of the gas due to the intruder is assumed small and a perturbation expansion is used. The gas is assumed to be initially at rest. A derivation for the first and second order stopping force on an projectile due to the induced charge density of the target is given. Structure factors are introduced to capture the physics relating to the structure of the projectile and to allow maximum flexibility and generalization. The second order stopping force is calculated using a novel ”holepunch” integration method and is compared to other available methods. Results are obtained for the case of a dicluster of protons which are colinear with their direction of motion as well as for a dicluster of protons which are randomly oriented incident on an aluminum target and compared to the single proton case.

The discovery of carbon nanotubes by Iijima in 1991 has created a torrent of new research activities. Research on carbon nanotubes ranges from studying their fundamental properties, such as their electron band structure and plasma frequencies, to developing new applications, such as self-assembled nano-circuits and field emission displays. Robust models are now needed to enable a better understanding of the electronic response of carbon nanotubes. We use time-dependent density functional theory to derive a two-fluid two-dimensional (2D) hydrodynamic model describing the collective response of a multiwalled carbon nanotube with dielectric media embedded inside or surrounding the nanotube. We study plasmon hybridization of the nanotube system in the UV range, the stopping force for ion channelling, the dynamical image potential for fast ions, channelled diclusters and point dipoles, and the energy loss for ions with oblique trajectories. Comparisons are made of results obtained from the 2D hydrodynamic model with those obtained from an extension of the 3D Kitagawa model to cylindrical geometries.

The discovery of carbon nanotubes by Iijima in 1991 has created a torrent of new research activities. Research on carbon nanotubes ranges from studying their fundamental properties, such as their electron band structure and plasma frequencies, to developing new applications, such as self-assembled nano-circuits and field emission displays. Robust models are now needed to enable a better understanding of the electronic response of carbon nanotubes. We use time-dependent density functional theory to derive a two-fluid two-dimensional (2D) hydrodynamic model describing the collective response of a multiwalled carbon nanotube with dielectric media embedded inside or surrounding the nanotube. We study plasmon hybridization of the nanotube system in the UV range, the stopping force for ion channelling, the dynamical image potential for fast ions, channelled diclusters and point dipoles, and the energy loss for ions with oblique trajectories. Comparisons are made of results obtained from the 2D hydrodynamic model with those obtained from an extension of the 3D Kitagawa model to cylindrical geometries.