低能碱金属离子散射测量金纳米团簇电荷分布的不均匀性
Inhomogeneous Charge Distribution Across Gold Nanoclusters Measured by Scattered Low Energy Alkali Ions
摘要：
低能量的Na $^+$和Li $^+$离子从Au纳米团簇散射的中和通过沉积到氧化物表面上形成的团簇尺寸的增加而降低。对这种现象的解释是基于团簇中的原子不是均匀带电的，而是边缘原子带正电，而中心原子几乎是中性的。这导致在边缘原子处向上指向的偶极子，其增加从这些原子散射的碱金属离子的中和概率。随着团簇尺寸的增加，边缘原子的数量相对于中心原子的数量减少，因此平均中和也减少。采用该模型的计算结果与实验数据进行了比较，并表明良好的协议，如果在边缘原子的偶极子的强度被假定为减少与集群的大小。该模型还解释了分散的Na $^+$和Li $^+$的中和概率的差异。
英文摘要：
The neutralization of low energy Na$^+$ and Li$^+$ ions scattered from Au nanoclusters formed by deposition onto oxide surfaces decreases as the cluster size increases. An explanation for this behavior is provided here, which is based on the notion that the atoms in the clusters are not uniformly charged, but that the edge atoms are positively charged while the center atoms are nearly neutral. This leads to upward pointing dipoles at the edge atoms that increase the neutralization probability of alkali ions scattered from those atoms. As the clusters increase in size, the number of edge atoms relative to the number of center atoms decreases, so that that the average neutralization also decreases. Calculations employing this model are compared to experimental data and indicate good agreement if the strengths of the dipoles at the edge atoms are assumed to decrease with cluster size. This model also explains differences in the neutralization probabilities of scattered Na$^+$ and Li$^+$.
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