The sinking of alkali cations in superfluid 4He nanodroplets is investigated theoretically using liquid 4He time-dependent density functional theory at zero temperature. The simulations illustrate the dynamics of the buildup of the first solvation shell around the ions. The number of helium atoms in this shell is found to linearly increase with time during the first stages of the dynamics. This points to a Poissonian capture process, as concluded in the work of Albrechtsen et al. on the primary steps of Na+ solvation in helium droplets [Albrechtsen et al., Nature 623, 319 (2023)]. The energy dissipation rate by helium atom ejection is found to be quite similar between all alkalis, the main difference being a larger energy dissipated per atom for the lighter alkalis at the beginning of the dynamics. In addition, the number of helium atoms in the first solvation shell is found to be lower at the end of the dynamics than at equilibrium for both Li+ and Na+, pointing to a kinetic rather than thermodynamical control of the snowball size for small and strongly attractive ions.

中文翻译：

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超流氦纳米液滴中碱离子的时间分辨溶剂化

使用零温度下液体 4He 时间相关密度泛函理论，从理论上研究了超流体 4He 纳米液滴中碱金属阳离子的下沉。模拟说明了离子周围第一溶剂化壳层形成的动力学。人们发现，在动力学的第一阶段，该壳层中的氦原子数量随着时间线性增加。正如 Albrechtsen 等人的工作中得出的结论，这指向泊松捕获过程。关于氦液滴中 Na+ 溶剂化的主要步骤 [Albrechtsen et al., Nature 623, 319 (2023)]。发现所有碱金属之间氦原子喷射的能量耗散率非常相似，主要区别在于较轻的碱金属在动力学开始时每个原子耗散的能量较大。此外，发现 Li+ 和 Na+ 的第一个溶剂化壳层中的氦原子数量在动力学结束时比平衡时要低，这表明对于小而强吸引力的雪球尺寸是动力学而非热力学控制。离子。