Based on molecular dynamics (MD) simulations, we explore the efficiency of molecular hydrogen as a tamper material in X-ray diffraction imaging of single nanoparticles. An \(\hbox {Ar}_{55}\) cluster serves as a model system for a nanoparticle which is embedded in a hydrogen shell of various sizes. The MD model accounts for the initial photoionization and Auger electron emission of the \(\hbox {Ar}_{55}\) core, the secondary field and impact ionizations in the core and in the tamper shell, and the neutralization of the electron deficiency in the core by the fast migration of electrons from the tamper shell to the core. We find that a low first ionization potential is crucial for a massive electron migration and thus for the efficiency of the tamper material. Accordingly, hydrogen is a much more efficient tamper material than the isoelectronic helium, for which we have performed comparative simulations. To fully exploit the tamper effect of hydrogen, the core must be completely embedded by the tamper shell. In this context, it is encouraging that Kuma et al. (J Phys. Chem. A 115, 7392 (2011) showed that it is possible to coat a sample by hydrogen inside helium nanodroplets. While water with its even lower first ionization potential is the natural tamper material for biological samples, hydrogen could be an alternative in material science.

基于分子动力学 (MD) 模拟，我们探索了分子氢作为篡改材料在单个纳米粒子的 X 射线衍射成像中的效率。一个\（\ hbox中的Ar {} _ {55} \）簇用作用于被嵌入在各种尺寸的一个氢壳的纳米颗粒的模型系统。MD 模型解释了\(\hbox {Ar}_{55}\)的初始光电离和俄歇电子发射核心、核心和篡改壳中的二次场和碰撞电离，以及通过电子从篡改壳到核心的快速迁移来中和核心中的电子缺陷。我们发现低第一电离电位对于大量电子迁移以及篡改材料的效率至关重要。因此，氢是一种比等电子氦更有效的篡改材料，我们已经对其进行了比较模拟。为了充分利用氢的篡改效应，核心必须完全被篡改外壳嵌入。在这种情况下，令人鼓舞的是 Kuma 等人。(J Phys. Chem. A 115, 7392 (2011) 表明，可以用氦纳米液滴内的氢涂覆样品。