氦纳米液滴上异核碱金属二聚体的激光诱导库仑爆炸
Laser-induced Coulomb explosion of heteronuclear alkali dimers on helium nanodroplets
AI总结：
本文利用符合过滤方法从同核与异核碱金属二聚体混合物的库仑爆炸信号中分离出异核二聚体的动能分布，并据此确定核间距分布，以 LiK 和 NaK 为例验证了方法有效性。
摘要：
位于氦纳米液滴表面的碱金属同核二聚体 Ak$_2$、Ak$^{\prime}_2$ 与异核二聚体 AkAk$^{\prime}$ 的样品混合物，在被强 50 fs 激光脉冲诱导双电离后，发生库仑爆炸，生成原子碱金属阳离子对 (Ak$^{+}$,Ak$^{+}$)、(Ak$^{\prime +}$,Ak$^{\prime +}$) 和 (Ak$^{+}$, Ak$^{\prime +}$)。测得的 Ak$^{+}$ 和 Ak$^{\prime +}$ 碎片离子的动能分布 $P(E_{\text{kin}})$ 中，包含来自同核和异核二聚体库仑爆炸贡献的重叠峰。利用基于每个库仑爆炸事件中两个碎片离子之间动量分配的符合过滤方法，我们证明，对于 Ak$^{+}$ 和 Ak$^{\prime +}$ 碎片离子，都可以分别提取出来自异核或同核二聚体的离子的单独 $P(E_{\text{kin}})$。该过滤方法通过结合速度图成像光谱仪和 TPX3CAM 探测器，同时探测 Ak$^{+}$ 和 Ak$^{\prime +}$ 离子的二维速度图像来实现。关键发现是，尽管同核二聚体同时存在，异核碱金属二聚体的 $P(E_{\text{kin}})$ 仍可被区分。根据 $P(E_{\text{kin}})$，我们通过库仑爆炸成像原理确定了核间距分布 $P(R)$。我们报告了 LiK 和 NaK 的结果，但我们的方法也应适用于其他异核二聚体，并可用于区分同核二聚体的不同同位素异形体。
英文摘要：
A sample mixture of alkali homonuclear dimers, Ak$_2$ and Ak$^{\prime}_2$ and heteronuclear dimers, AkAk$^{\prime}$, residing on the surface of helium nanodroplets are Coulomb exploded into pairs of atomic alkali cations, (Ak$^{+}$,Ak$^{+}$), (Ak$^{\prime +}$,Ak$^{\prime +}$), (Ak$^{+}$, Ak$^{\prime +}$), following double ionization induced by an intense 50 fs laser pulse. The measured kinetic energy distribution $P(E_{\text{kin}})$ of both the Ak$^{+}$ and the Ak$^{\prime +}$ fragment ions contains overlapping peaks due to contributions from Coulomb explosion of the homonuclear and the heteronuclear dimers. Using a coincident filtering method based on the momentum division between the two fragment ions in each Coulomb explosion event, we demonstrate that the individual $P(E_{\text{kin}})$ pertaining to the ions from either the heteronuclear or from the homonuclear dimers can be retrieved, for both the Ak$^{+}$ and for the Ak$^{\prime +}$ fragment ions. This filtering method works through the concurrent detection of two-dimensional velocity images of the Ak$^{+}$ and the Ak$^{\prime +}$ ions implemented through the combination of a velocity map imaging spectrometer and a TPX3CAM detector. The key finding is that $P(E_{\text{kin}})$ for heteronuclear alkali dimers can be distinguished despite the simultaneous presence of homonuclear dimers. From $P(E_{\text{kin}})$ we determine the distribution of internuclear distances $P(R)$ via the Coulomb explosion imaging principle. We report results for LiK and for NaK but our method should should also work for other heteronuclear dimers and for differentiating between different isotopologues of homonuclear dimers.
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