Influence of Image Charges on the Transport of Low-Energy Ions in Rhombic Micropores
Authors: Sun Wen-Sheng  , Yuan Hua  , Liu En-Shun  , Du Zhan-Hui  , Pan Yu-Zhou  , Fan Xu-Hong  , Wang Qi-Jun  , Zhao Zhan-Yan  , Cheng Qian  , Wan Cheng-Liang  , Cui Ying  , Zhu Li-Ping  , Li Peng-Fei  , Wang Tian-Qi  , Yao Ke  , Reinhold Schuch  , Fang Tie-Feng  , Cheng Xi-Meng  , Zhang Hong-Qiang  ,   1 The School of Physical Science and Technology, Nantong University, Nantong, 226019, China;,   2 The School of Nuclear Science and Technology, Lanzhou University, Lanzhou, 730000, China;,   3 College of Nuclear Science and Technology, Harbin Engineering University, Harbin 150001, China;,   4 Institute of Space Environment and Material Science, Harbin Institute of Technology, Harbin 150006, China;,   5 Center for Advanced Science of Rare Isotopes, Lanzhou University, Lanzhou 730000, China;,   6 School of Basic Medical Sciences, Lanzhou University, Lanzhou 730000, China;,   7 Institute of Modern Physics, Fudan University, Shanghai, 200433, China;,   8 Department of Physics, Stockholm University, Stockholm S-10691, Sweden
Published: February 2025

The study of low-energy, high-charge-state ions traversing insulating nanochannels has focused on the guiding effects due to the deposition of charge, while experimental and theoretical research on the influence of image charge forces caused by the polarization of the channel walls during ion transmission is relatively scarce. We employed a combination of experimental and theoretical methods to conduct experiments on 1 keV N<sub>2</sub><sup>+</sup> ion beams passing through muscovite microporous membranes. Under the condition of complete discharge of the microporous membrane, we measured the two-dimensional angular distribution of ejected ions at the initial stage of ion beam incidence at a zero-degree inclination. In previous simulation calculations, to simplify the calculation process, first-order image force approximation and static approximation were used to calculate the image charge forces. We found that the results obtained from these calculations still differ from the experimental results. Therefore, we refined the calculation formula for image charge forces, taking into account the full effect of these forces.In previous studies on image charge forces, we neglected the impact of ion velocity on the polarization of the channel walls. We used the surface dielectric response theory of the image force experienced by ions within the micropores, which depends on ion velocity and the distance between the ion and the channel wall, to simulate and calculate the experimental results. We studied the influence of image charge forces caused by surface dielectric response due to ion velocity on the angular distribution of ejected ions. We found discrepancies between the simulated and experimental two-dimensional angular distributions, with the experimental results showing a wider half-height width than the simulated results.<br>To explore the effects of beam divergence and the angle between the micropore axis and the beam on ion penetration and the two-dimensional angular distribution of ejected ions, we conducted simulation calculations for 1 keV N<sub>2</sub><sup>+</sup> under different beam conditions, considering third-order dynamic image charge forces. We analyzed several potential influences in the simulation calculations and assessed the impact of the true state of the beam and the angle between the beam and the micropore on the differences between simulation and experiment. This work provides the possibility of studying the surface dielectric response of micropores using ion beams as probes.