Anomalous Positive Ion Formation in Negative Ion Collisions with HOPG
| Autor: | Feifei Xiong, Jianjie Lu, Shunli Qiu, Fei Ren, Hao-Yu Jiang, Guopeng Li, Yanling Guo, Yiran Liu, Bin Ding, Lei Gao, Pinyang Liu, Lin Chen, Ximeng Chen, Yuefeng Liu, Yunqing Xiao |
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| Rok vydání: | 2016 |
| Předmět: |
Fusion
Chemistry Scattering chemistry.chemical_element 02 engineering and technology 021001 nanoscience & nanotechnology 01 natural sciences Surfaces Coatings and Films Electronic Optical and Magnetic Materials Ion Molecular dynamics General Energy Highly oriented pyrolytic graphite 0103 physical sciences Fluorine Graphite Physical and Theoretical Chemistry Atomic physics 010306 general physics 0210 nano-technology Scaling |
| Zdroj: | The Journal of Physical Chemistry C. 120:18538-18547 |
| ISSN: | 1932-7455 1932-7447 |
| Popis: | Charge transfer on graphite, a typical substrate and one of the fusion first wall materials, is of great importance in the plasma–wall interaction, thin-film growth, and surface catalysis. We present an experimental study of 8.5–22.5 keV energy carbon, oxygen, and fluorine negative ions scattering from a highly oriented pyrolytic graphite (HOPG) surface at a scattering angle of 8°. It is found that the positive ion fraction decreases monotonically with the increase of both incident velocity and angle. In particular, these dependences are very different from those presented in previous studies. A molecular dynamics simulation reveals that, around the critical condition for planar surface channeling, a number of projectiles may penetrate into the subsurface and become energetic atoms when they emerge from the surface. Hence, an exponential scaling related to the penetration probability has been proposed to well describe the velocity and angle dependences of positive ion fractions. |
| Databáze: | OpenAIRE |
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