Multicharged Ion Impact on Clean Au(111): Suppression of Kinetic Electron Emission in Glancing Angle Scattering
Multicharged Ion Impact on Clean Au(111): Suppression of Kinetic Electron Emission in Glancing Angle Scattering
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DOI：
10.1103/physrevlett.81.1965
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发表时间：
1998-08
影响因子：
8.6
通讯作者：
C. Lemell;Johannes Stockl;J. Burgdörfer;G. Betz;H. Winter;F. Aumayr
中科院分区：
文献类型：
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作者：
C. Lemell;Johannes Stockl;J. Burgdörfer;G. Betz;H. Winter;F. Aumayr
本文测量了多电荷慢Ar离子掠入射在Au（111）表面上的发射电子数统计和入射散射角分布。不同的弹丸出口和入射角的电子统计谱的比较允许分离的潜在和动力学电子发射。一个分子动力学模拟允许关联的多个电子发射与特定的轨迹历史（平面和次表面沟道，与目标原子在步骤和缺陷的密切碰撞）。[S0031 - 9007（98）06964 - 6] PACS编号：79.20.Rf，61.85。+ p，79.60.Bm慢速高电荷离子（HCI）与清洁表面的相互作用揭示了新的现象，如奇异"空心原子"的瞬时形成[1 - 5]和最近发现的"电势溅射"效应[6]。在表面以上，空心原子的形成和演化可以通过经典的越垒（COB）模型[1，7]进行理论描述。该模型预测的图像能量增益和空心原子形成的距离可以在几个独立的实验中得到验证[8 - 10]。空心原子形成和衰变的其他特征，如潜在的电子发射（PE）[11]，通常被表面下相互作用过程的显著贡献所掩盖，特别是在动能发射现象占主导地位的较高射弹能量下[12]。因此，到目前为止，大多数这样的结果只能作为COB模型的间接证明。我们已经开发出一种实验方法，使我们能够区分电子发射诱导以上（或在）的表面从下面的表面发射。这一信息又可区分动力排放和潜在排放。在这项工作中，我们相关的多电荷氩离子在清洁的金属表面与特定的弹丸轨迹，其特征在于所产生的散射角的掠入射散射过程中发射的电子，以实现分离的上面和下面的表面发射。与垂直入射的电子发射数据进行比较，具有相同的射弹、电荷状态和具有垂直于表面的相等速度的靶物质，允许直接识别电势和动力学电子发射
We have measured the number statistics of emitted electrons in coincidence with the projectile scattering angle distribution for multiply charged slow Ar ions scattered off an Au(111) surface at grazing incidence. The comparison of the electron statistic spectra for different projectile exit and incidence angles permits a separation of potential and kinetic electron emission. A molecular dynamics simulation allows to associate the multiple electron emission with specific trajectory histories (planar and subsurface channeling, close collisions with target atoms at steps and imperfections). [S0031-9007(98)06964-6] PACS numbers: 79.20.Rf, 61.85. + p, 79.60.Bm The interaction of slow highly charged ions (HCI) with clean surfaces reveals new phenomena like the transient formation of exotic “hollow atoms” [1 ‐5] and the recently discovered effect of “potential sputtering” [6]. Above the surface the formation and evolution of hollow atoms can be described theoretically by the classical over-the-barrier (COB) model [1,7]. The image energy gain and the distance of hollow atom formation predicted by this model could be verified in several independent experiments [8‐ 10]. Other signatures of hollow atom formation and decay like potential electron emission (PE) [11] are often masked by significant contributions from below surface interaction processes, in particular, at higher projectile energies where kinetic emission phenomena become dominant [12]. So far, most such results could therefore be used only as indirect proof for the COB model. We have developed an experimental approach which enables us to distinguish between electron emission induced above (or at) the surface from below surface emission. This information can, in turn, provide distinction between kinetic and potential emission. In this work we correlate the electrons emitted during grazing incidence scattering of multiply charged argon ions at a clean metal surface with specific projectile trajectories characterized by the resulting scattering angle, to achieve a separation of above and below surface emission. A comparison with electron emission data for normal incidence with the same projectile, charge state, and target species having equal velocity normal to the surface allows the direct identification of potential and kinetic electron emission