Transmission Of Slow-nonmetallic Negative Ions In Al₂O₃ Nanocapillaries

The transmission of 10keV to 18keV Cl^- ions through Al₂O₃ nanocapillaries with 50nm in diameter, 7μm in length and 50nm in diameter, 12μm in length is studied respectively in this work. Angular distribution and charge state distribution of transmitted particles are measured when capillaries are tilted with respect to incident ion beam. According to the angular distribution of transmitted ions, the charge states distribution, relative intensities of transmitted ions and angular distribution width of different charge state ions, several new phenomena are found:1. Two peaks are found in angular distribution spectrum of transmitted particle: one kept at 0°and another moved when the tilt angle changed. Particles in the peak of 0°is composed by Cl^- ions, another one is almost composed by Cl⁰ and Cl⁺ ions;2. The intensity of transmitted particles decreases when the tilt angle increases, and the thicker the capillaries is, the faster the intensity decreases;3. For a given incident energy and nanocapillary, intensity of Cl^- in transmitted particles decreases fastest, the second is Cl⁰, and the third is Cl⁺;4. When the tilt angle increases, the fraction of Cl^- in transmitted particles decreases, but fractions of Cl⁰ and Cl⁺ grow up;5. For the width of angular distribution for different charge-state ions in transmitted particles, Cl^- is the narrowest, the second is Cl⁰, and the third is Cl⁺.According to results of the experiment, several conclusions are obtained:1. Transmitted particles can be divided into two parts: one part is composed by projectiles which has no collision with inner walls of nanocapillary, another one is composed by scattered ions;2. Transmitted ions which have not collided with nanocapillaries preserved its initial charge state, but most scatted ions have exchanged electrons with inner walls of nanocapillary and turned into Cl⁰ and Cl⁺ ions;3. The transmission direction of scattered ions agree with the axis of nanocapillary very well, and the more ions were scattered, the wider the angular it would be;4. Most scattered ions are caused by elastic collisions between ions and inner walls of nanocapillary, a few of them are scatted by electrostatic field which referred to guiding effect;5. For the same diameter nanocapillaries, the thicker the capillary is, the stronger the focusing effect is, and the more obvious regulation it has.