Probing charge-transfer processes in helium nanodroplets by optically selected mass spectrometry (OSMS): charge steering by long-range interactions.
Probing charge-transfer processes in helium nanodroplets by optically selected mass spectrometry (OSMS): charge steering by long-range interactions.
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通过光选质谱 (OSMS) 探测氦纳米液滴中的电荷转移过程：通过长程相互作用进行电荷转向。
DOI：
10.1021/ja042489s
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发表时间：
2005
影响因子：
15
通讯作者：
Roger E. Miller
中科院分区：
文献类型：
--
作者：
William K. Lewis;C. Michael Lindsay;R. Bemish;Roger E. Miller
氦纳米液滴中氦原子的电子碰撞电离随后发生快速电荷迁移，最终导致电荷定位在原子或分子溶质上。这里使用我们称为光选质谱 (OSMS) 的新实验方法，针对氦中的氰化氢、乙炔和氰基乙炔的情况研究了该过程。该方法将红外激光光谱与质谱分析相结合，将给定条件下存在的各种物质对整个液滴束质谱的贡献分开。这是通过振动激发液滴子集中存在的特定物质（例如，包含单个 HCN 分子的液滴）来完成的。由此产生的氦气蒸发导致这些液滴的电离截面随之减小。该方法用于研究氦中的电荷迁移，并揭示电荷转移到溶剂化分子的概率对于小液滴而言并不接近统一，并且取决于溶剂化分子的身份。通过考虑静电势（电荷和嵌入分子之间）对迁移电荷轨迹的影响，定量地解释了实验结果。
Electron impact ionization of a helium atom in a helium nanodroplet is followed by rapid charge migration, which can ultimately result in the localization of the charge on an atomic or molecular solute. This process is studied here for the cases of hydrogen cyanide, acetylene, and cyanoacetylene in helium, using a new experimental method we call optically selected mass spectrometry (OSMS). The method combines infrared laser spectroscopy with mass spectrometry to separate the contributions to the overall droplet beam mass spectrum from the various species present under a given set of conditions. This is done by vibrationally exciting a specific species that exists in a subset of the droplets (for example, the droplets containing a single HCN molecule). The resulting helium evaporation leads to a concomitant reduction in the ionization cross sections for these droplets. This method is used to study the charge migration in helium and reveals that the probability of charge transfer to a solvated molecule does not approach unity for small droplets and depends on the identity of the solvated molecule. The experimental results are explained quantitatively by considering the effect of the electrostatic potential (between the charge and the embedded molecule) on the trajectory of the migrating charge.