J. Heyrovský Institute of Physical Chemistry v.v.i., Academy of Sciences of the Czech Republic, Dolejškova 3, 18223 Prague, Czech Republic.
J Chem Phys. 2013 Dec 7;139(21):214308. doi: 10.1063/1.4834715.
We investigate the electron ionization of clusters generated in mixed Ar-water expansions. The electron energy dependent ion yields reveal the neutral cluster composition and structure: water clusters fully covered with the Ar solvation shell are formed under certain expansion conditions. The argon atoms shield the embedded (H2O)n clusters resulting in the ionization threshold above ≈15 eV for all fragments. The argon atoms also mediate more complex reactions in the clusters: e.g., the charge transfer between Ar(+) and water occurs above the threshold; at higher electron energies above ~28 eV, an excitonic transfer process between Ar(+)* and water opens leading to new products Ar(n)H(+) and (H2O)(n)H(+). On the other hand, the excitonic transfer from the neutral Ar* state at lower energies is not observed although this resonant process was demonstrated previously in a photoionization experiment. Doubly charged fragments (H2O)(n)H2(2+) and (H2O)(n)(2+) ions are observed and Intermolecular Coulomb decay (ICD) processes are invoked to explain their thresholds. The Coulomb explosion of the doubly charged cluster formed within the ICD process is prevented by the stabilization effect of the argon solvent.
我们研究了在混合 Ar-水膨胀中生成的团簇的电子电离。电子能量相关的离子产率揭示了中性团簇的组成和结构：在一定的膨胀条件下，形成了完全被 Ar 溶剂化壳覆盖的水团簇。氩原子屏蔽嵌入的（H2O）n 团簇，导致所有碎片的电离阈值都在 ≈15 eV 以上。氩原子还在团簇中介导更复杂的反应：例如，Ar(+)和水之间的电荷转移发生在阈值以上；在更高的电子能量（约 28 eV 以上），Ar(+)* 和水之间的激子转移过程打开，导致新的产物 Ar(n)H(+) 和 (H2O)(n)H(+)。另一方面，尽管先前在光致电离实验中证明了中性 Ar* 态的激子转移，但在较低能量下没有观察到这种过程。观察到了双重电荷碎片（H2O）(n)H2(2+)和 (H2O)(n)(2+)离子，并引入了分子间库仑衰变（ICD）过程来解释它们的阈值。ICD 过程中形成的双重电荷团簇的库仑爆炸被氩溶剂的稳定化效应所阻止。
