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首页> 外文期刊>The Journal of Chemical Physics >Theoretical investigation of nonadiabatic and internal temperature effects on the collision-induced multifragmentation dynamics of Na-5(+) cluster ions
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Theoretical investigation of nonadiabatic and internal temperature effects on the collision-induced multifragmentation dynamics of Na-5(+) cluster ions

机译：非绝热和内部温度对Na-5（+）团簇离子碰撞诱导多碎片动力学的影响的理论研究

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摘要

In a continued effort to disentangle adiabatic, nonadiabatic, and internal temperature effects in the collision-induced multifragmentation of alkali-metal cluster ions at moderate energies, we report a theoretical study of this process for the Na-5(+)+He encounter in the 100 eV (center-of-mass) collision energy range. The investigation makes use of a diatomics-in-molecules based nonadiabatic molecular-dynamics (NAMD) method. All of the ten electronic (1)A(') molecular states of the cluster that can be formed by assembling ground-state monomers are considered explicitly. Cross sections for the corresponding 12 possible fragmentation channels are determined. As in the Na-4(+)+He case, we find that a few-channel characteristic of adiabatic fragmentation in the electronic ground state dominates. This owes primarily to the dominance of impulsive adiabatic mechanisms. Nonetheless, two significant nonadiabatic transitions take place: electronic excitation during the collision and electronic deexcitation in the postcollision stage. A large amount of the electronic excitation subsequently relaxes into the electronic ground state during the postcollision stage. This important intramolecular vibrational relaxation (IVR)-type mechanism enhances the population of channels characteristic of adiabatic fragmentation in the electronic ground state. The populations of the fragmentation channels are quite sensitive to the internal cluster temperature. This is discussed in terms of the conditions of occurrence of the fragmentation mechanisms and their competition. Comparisons with experimental results are presented and discussed.
机译：为了继续解决在中等能量下碰撞诱导的碱金属簇离子的多碎片化过程中的绝热，非绝热和内部温度效应，我们报道了Na-5（+）+ He在此过程中的理论研究。 100 eV（质量中心）碰撞能量范围。该研究利用了基于分子双原子的非绝热分子动力学（NAMD）方法。明确考虑了可以通过组装基态单体形成的簇的所有十个电子（1）A（'）分子态。确定对应的12种可能的碎裂通道的横截面。与Na-4（+）+ He的情况一样，我们发现电子基态中的绝热碎片的几个通道特性占主导。这主要归因于脉冲绝热机理的主导。但是，发生了两个重要的非绝热转变：碰撞过程中的电子激发和碰撞后阶段的电子去激励。在碰撞后阶段，大量的电子激励随后放松到电子基态。这种重要的分子内振动弛豫（IVR）型机制可增强电子基态中绝热片段化特征的通道总数。碎片通道的数量对内部簇的温度非常敏感。将根据碎片机制的发生条件及其竞争对它们进行讨论。提出并讨论了与实验结果的比较。

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