Simulations and analytic models of ion guiding through a nanocapillary in insulating polymers

The guiding of highly charged ions through a single cylindrical nanocapillary is simulated to compare with previous experiments using capillaries in polyethylene terephthalate (PET) and polycarbonate (PC) polymers. The ions move in the three-dimensional electric field produced by the charges that ions have deposited before. Guiding conditions are achieved, using a nonlinear conductivity law to transport the deposited charges along the capillary surface. Remarkably, it is found that the migration of the deposited charges perpendicular to the capillary axis has a bigger effect on maintaining the ion guiding than the transport parallel to it. The ion trajectories are found to be focused, enhancing the ion guiding. The mean angle of the transmitted ions exhibit pronounced oscillations, in agreement with previous measurements. Experimentally observed differences in the oscillatory frequency as well as partial blocking of the ion transmission are interpreted by the calculations using a larger conductivity for PC in comparison with PET. Emphasis is given to the understanding of the self-organized formation of the charge patches.