Department of Chemistry, University of Leicester, University Road, Leicester, LE1 7RH, United Kingdom.
J Phys Chem A. 2011 Jun 30;115(25):7010-6. doi: 10.1021/jp112204e. Epub 2011 May 18.
Electron impact ionization of helium nanodroplets containing a dopant, M, can lead to the detection of both M(+) and helium-solvated cations of the type M(+)·He(n) in the gas phase. The observation of helium-doped ions, He(n)M(+), has the potential to provide information on the aftermath of the charge transfer process that leads to ion production from the helium droplet. Here we report on helium attachment to the ions from four common diatomic dopants, M = N(2), O(2), CO, and NO. For experiments carried out with droplets with an average size of 7500 helium atoms, the monomer cations show little tendency to attach and retain helium atoms on their journey out of the droplet. By way of contrast, the corresponding cluster cations, M(n)(+), where n ≥ 2, all show a clear affinity for helium and form He(m)M(n)(+) cluster ions. The stark difference between the monomer and cluster ions is attributed to more effective cooling of the latter in the aftermath of the ionization event.
氦纳米液滴中掺杂剂 M 的电子碰撞电离，可导致在气相中同时检测到 M(+)和氦溶剂化阳离子类型 M(+)·He(n)。氦掺杂离子 He(n)M(+)的观测有可能提供有关导致氦液滴中产生离子的电荷转移过程后续情况的信息。在这里，我们报告了四种常见双原子掺杂剂 M = N(2)、O(2)、CO 和 NO 的离子与氦的附着情况。对于用平均大小为 7500 个氦原子的液滴进行的实验，单体阳离子几乎没有附着和保留氦原子的趋势，在离开液滴的过程中。相比之下，相应的团簇阳离子 M(n)(+)（其中 n ≥ 2）都表现出对氦的明显亲和力，并形成 He(m)M(n)(+)团簇离子。单体和团簇离子之间的明显差异归因于在电离事件发生后后者的冷却效率更高。
