【作者】 孙光智；

【导师】 陈熙萌；

【作者基本信息】 兰州大学 ， 粒子物理与原子核物理， 2009， 博士

【摘要】 本论文采用能量为10～18keV的Cl^-离子分别与孔径为50nm、厚7μm和孔径为50nm、厚12μm的Al₂O₃微孔膜相互作用,研究低能非金属性负离子穿过绝缘体纳米微孔膜时的物理过程。测量了微孔膜与入射束流在不同夹角下,Cl^-穿过Al₂O₃微孔膜后的角分布和电荷态分布。通过对透射离子角分布谱形状、电荷态分布、不同价态的透射离子相对强度、半高宽等的研究,发现了新的物理现象:1.透射离子角分布呈明显的双峰,其中一个峰保持在0°位置不变,另一个随着偏转角变化而变化。0°位置的峰主要由Cl^-组成,而偏离0°的峰主要由Cl⁰和Cl⁺组成;2.透射离子的强度随偏转角增大而减小,且膜越厚,下降越快。3.透射离子中,Cl^-强度下降最快,其次是Cl⁰,再是Cl⁺;4.随着偏转角增大,透射离子中Cl^-所占的份额在减小,Cl⁰和Cl⁺所占的份额逐渐增加;5.不同价态的透射离子的角分布,Cl^-最窄,其次为Cl⁰,Cl⁺最宽;入射离子能量越高,角分布越窄;通过对实验结果的分析,得到了如下结论:1.透射离子可以分为与孔壁未经过任何散射而直接穿过微孔膜的离子和与孔壁经过散射后射出小孔的离子;2.直接透射的离子未与微孔膜发生电荷转移,仍保持Cl^-不变,而与孔壁发射散射（碰撞）的离子绝大部分发生电荷转移,变为Cl⁰和Cl⁺,少量保持Cl^-不变;3.发生散射的离子的出射方向与孔轴向一致,且散射次数越多,角分布越宽;4.散射离子中有一部分是与孔壁发生了弹性散射,少量保持Cl^-价态不变的离子是由孔壁积累的电荷形成的电场对入射离子散射造成的,即“导向作用”引起的;5.相同孔径的微孔膜,孔越长,孔对离子的聚焦作用越强,透射离子的规律性越强。更多还原

【Abstract】 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.更多还原