(e,e+ion) study on electron-induced dissociative ionization of O2
(e,e+ion) study on electron-induced dissociative ionization of O2
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DOI：
10.1103/physreva.99.022704
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发表时间：
2019-02
影响因子：
2.9
通讯作者：
N. Watanabe;S. Yamada;M. Takahashi
中科院分区：
文献类型：
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作者：
N. Watanabe;S. Yamada;M. Takahashi
电子诱导分子解离电离是碰撞物理和分子物理中的一个基本过程。在电子碰撞电离中，一部分入射电子能量被转移到靶上，并分布在分子离子的内能和弹射电子的动能中。如果内能足够高，分子阳离子可以衰变成离子和中性碎片。解离电离也通过光电离发生，但光诱导过程和电子诱导过程之间存在本质区别，后者不受偶极子选择规则的限制，电四极子和更高的多极子跃迁有助于反应，取决于从入射电子转移到目标的动量的大小。分子氧的解离电离是高能碎片物质的重要来源，在行星大气和实验室等离子体b[1]的物理和化学过程中起着至关重要的作用。为了详细了解O2的解离电离，多年来进行了各种各样的电子冲击研究[1-10]。生成O+的部分电离截面已经通过离子产率测量[2-4]确定，O+的动能（KE）分布已经使用飞行时间技术[5,6]和最近的速度图成像方法[7]进行了测量。已经观察到多峰KE分布[5-9]，表明存在四个主要的O+基团，其峰值能量为KE= 0。8、2、3和5 eV b[1]，尽管由于它们的贡献b[7]的显著重叠，很难从数据中解卷积单个电离通道。尽管困难重重，0.8 eV的峰值已经明确
Electron-induced dissociative ionization of molecules is a fundamental process in collision physics and molecular physics. In electron-impact ionization, a portion of the incident electron energy is transferred to the target and distributed among the internal energy of the molecular ion and the kinetic energy of the ejected electron. The molecular cation may, if the internal energy is sufficiently high, decay into ionic and neutral fragments. Dissociative ionization occurs also via photoionization, but there is an essential difference between the photo-and electron-induced processes, where the latter is not restricted by the dipole selection rules and electric quadrupole and higher multipole transitions contribute to the reaction, depending upon the magnitude of momentum transferred from the incident electron to the target. The dissociative ionization of molecular oxygen is an important source of energetic fragment species that play crucial roles in physical and chemical processes in planetary atmospheres and laboratory plasmas [1]. To get detailed knowledge of the dissociative ionization of O2, various kinds of electronimpact studies have been conducted over the years [1–10]. The partial ionization cross section for the production of O+ has been determined from ion-yield measurements [2–4], and the kinetic-energy (KE) distributions of O+ have been measured using a time-of-flight technique [5, 6] and, more recently, the velocity map imaging method [7]. Multipeaked KE distributions have been observed [5–9], suggesting the presence of four main O+ groups with peak energies of KE= 0. 8, 2, 3, and 5 eV [1], though there is difficulty in deconvoluting individual ionization channels from the data due to the significant overlapping of their contributions [7]. Despite the difficulty, the 0.8 eV peak has unambiguously