arXiv 2402.005872024-02-01physics.atm-clus

通过激光诱导库仑爆炸测定氦纳米液滴上碱金属三聚体的结构

Structure determination of alkali trimers on helium nanodroplets through laser-induced Coulomb explosion

Lorenz Kranabetter, Henrik H. Kristensen, Constant A. Schouder, Henrik Stapelfeldt

备注：: 7 pages, 5 figures

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AI总结：

本研究利用激光诱导库仑爆炸结合三重协方差分析与动能分布，测定了氦纳米液滴上Na₃、K₃、Rb₃的等边三角结构及平衡键长，解释了Na₃键长与理论值的差异，并得到核间距分布。

摘要：

位于He（氦）纳米液滴表面的碱金属三聚体Ak$_3$在强飞秒激光脉冲的多光子吸收后发生三重电离，裂解为三个关联的Ak$^+$离子。结合碎片离子发射方向的三重协方差分析信息及其动能分布$P(E_{\text{kin}})$，我们发现Na$_3$、K$_3$和Rb$_3$均为等边三角形结构，对应于能量最低的四重态$^{4}\text{A}_{2}'$的结构，并测定了平衡键长：$R_\text{eq}$(Na$_3$)=4.65±0.15 Å，$R_\text{eq}$(K$_3$)=5.03±0.18 Å，$R_\text{eq}$(Rb$_3$)=5.45±0.22 Å。对于K$_3$和Rb$_3$，这些数值与现有理论计算结果吻合良好；而Na$_3$的数值比现有理论结果大0.2-0.3 Å，该差异归因于Na$_3$在电离过程中存在微小的核间运动。此外，我们在键角固定的假设下测定了核间距分布$P(R)$，并将结果与核间波函数的平方$|Ψ(R)|^2$进行了比较。

英文摘要：

Alkali trimers, Ak$_3$, located on the surface of He nanodroplets are triply ionized following multiphoton absorption from an intense femtosecond laser pulse leading to fragmentation into three correlated Ak$^+$ ions. Combining the information from three-fold covariance analysis of the emission direction of the fragment ions and from their kinetic energy distributions $P(E_{\text{kin}})$, we find that Na$_3$, K$_3$, and Rb$_3$ have an equilateral triangular structure, corresponding to that of the lowest-lying quartet state $^{4}\mathrm{A}_{2}'$, and determine the equilibrium bond distance $R_\text{eq}$(Na$_3$) = 4.65 $\pm$ 0.15 Å, $R_\text{eq}$(K$_3$) = 5.03 $\pm$ 0.18 Å, and $R_\text{eq}$(Rb$_3$) = 5.45 $\pm$ 0.22 Å. For K$_3$ and Rb$_3$ these values agree well with existing theoretical calculations, while for Na$_3$ the value is 0.2-0.3 Å larger than the existing theoretical results. The discrepancy is ascribed to a minor internuclear motion of Na$_3$ during the ionization process. Also, we determine the distribution of internuclear distances $P(R)$ under the assumption of fixed bond angles. The results are compared to the square of the internuclear wave function $|Ψ(R)|^2$.

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