Transmission of 16 keV Cu− ions through Al2O3 nano-capillaries

The interaction of 16keV Cu− ions with Al2O3 nano-capillaries of 50nm diameter and 10μm length was studied. The angular and charge state distributions of the transmitted particles were measured by a position-sensitive microchannel plate detector. It shows that transmitted particles appear as two peaks and consist of three charge states, Cu−, Cu0 and Cu+. As the tilt angle increases, more Cu− ions lose electrons resulting in the formation of Cu0 and Cu+ during multiple collisions with the capillary walls. Unlike previously reported results on highly charged ions, keV-energy Cu− ions undergo significant charge exchange processes with the inner walls of the capillaries. This indicates that the guiding effect is absent in the negative ion transmission under the very low ion current conditions.