摘要
理论模拟结合实验研究了16-keVCl^(-)离子穿越不同厚度(7和12μm)的Al2O3微孔膜的物理过程,发现负离子传输中并不存在与正离子传输类似的明显的导向现象。在只考虑散射过程的情况下,模拟出的穿透粒子角分布及电荷态分布与实验结果符合很好,出射的Cl^(-)离子沿初束方向分布;Cl^(0)、Cl^(+)离子沿微孔轴向分布。仔细分析了不同出射粒子的角分布,发现出射的Cl^(+)在微孔轴向与初束方向之间分布;经单次散射出射的Cl^(0)沿微孔轴向分布,而经多次散射出射的Cl^(0)向初束方向移动。发现了Cl^(-)离子穿越不同厚度的具有相同微孔直径的Al2O3微孔时,较厚的膜出射的Cl^(+)/Cl^(0)比例低。理论分析显示,这是由散射过程的特性造成的,随着微孔膜厚度的增加,出射的Cl^(0)中经单次碰撞的比例变小,而多次散射出射的比例增加,从而导致Cl^(+)离子转化为Cl^(0)的几率要远大于Cl^(0)转化为Cl^(+)离子的几率,使得长的微孔出射的粒子中Cl^(+)/Cl^(0)比例低。
The transmission of 16-keVCl^(-)ions through Al2 O3 nanocapillaries of 7 and 12μm in thickness was studied both by experiment and simulation.It is found that the transmission of negative ions is different from that of positive ions through insulating nanocapillaries,where the deposited charges result in the so-called guiding effect.For the case of only the scattering,the transmitted angular distributions and charge state distributions from the simulations agreed well with the experimental results,i.e.,the transmittedCl^(-)ions exits to the direction of the primary beam;the transmitted Cl^(0)andCl^(-)spread around the axis of the capillaries.The analysis of the simulated trajectories shows that the transmitted Cl^(+)ions spans from the axis of nanocapillaries to the primary beam direction;the transmitted Cl^(0)due to the single scattering is centered around the axes of the nanocapillaries while the transmitted Cl^(0)through multiple scattering shifts to the direction from the axes of the capillaries to the primary beam direction.From the simulations,it is found that the ratio of Cl^(+)/Cl^(0)for the transmitted particles exited from the nanocapillaries of longer lengths is lower,in accord to the experiments.The increase of the length of the capillaries will lead to the drop of the portion of transmitted Cl^(0)by single scattering and the increase of the probability of the exiting of Cl^(0)through multiple scatterings.Therefore the probability of Cl^(+)ions changed to Cl^(0)is much larger than that Cl^(0)changed to Cl^(+)ions in the collision process,leading to the smaller ratio of Cl^(+)/Cl^(0)for the transmitted particles exited from the nanocapillaries of longer lengths.
作者
刘中林
哈帅
张文铭
谢一鸣
李鹏飞
靳博
张琦
马越
路迪
万城亮
崔莹
周鹏
张红强
陈熙萌
LIU Zhonglin;HA Shuai;ZHANG Wenming;XIE Yiming;LI Pengfei;JIN Bo;ZHANG Qi;MA Yue;LU Di;WANG Chengliang;CUI Ying;ZHOU Peng;ZHANG Hongqiang;CHEN Ximeng(School of Nuclear Science and Technology,Lanzhou University,Lanzhou 730000,China;School of Nuclear Engineering and Technology,North China Electric Power University,Beijing 102206,China;RIKEN Nishina Center,RIKEN,Wako,351-0198,Japan;Department of Physics,University of Gothenburg,SE-41296Gothenburg,Sweden)
出处
《原子核物理评论》
CAS
CSCD
北大核心
2021年第1期95-101,共7页
Nuclear Physics Review
基金
国家自然科学基金资助项目(U1732269)
瑞典科研与教育国际合作基金资助项目(STINT IB2018-8071)~~。
