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里德伯-基态分子由一个里德伯原子和一个基态原子组成, 束缚机制是里德伯电子与基态原子的低能电子散射相互作用. 理论上, 通过低能电子散射Fermi赝势模型, 数值计算了铯(36D 5/2+6S 1/2)里德伯-基态分子的绝热势能曲线, 提取了里德伯分子的束缚能和平衡核间距等光谱参数. 实验上, 利用双光子光缔合技术成功制备了散射三重态( TΣ, Triplet)和散射单重态-三重态混合( S,TΣ, Mixed)形成的里德伯-基态分子, 获得了里德伯分子的光缔合光谱, 测量的势阱深度与理论计算结果相吻合. 另外, 以散射三重态为例, 分析了里德伯分子的光缔合光谱在外加电场中的展宽现象, 获得其平均永久电偶极矩
$|\bar{d}|$ 为(12.10 ± 1.65) Debye ((4.76 ± 0.65) ea 0), 与理论计算结果保持一致. 该研究为实验上制备D态里德伯-基态分子提供了可行的实验方案, 对理解里德伯分子的光谱特性具有重要意义.-
关键词:
- 超冷里德伯-基态分子/
- 光缔合光谱/
- 绝热势能曲线/
- 电偶极矩
Ultra-cold long-range Rydberg molecules, consisting of a Rydberg atom and a ground-state atom or another Rydberg atom or ion, have attracted considerable attention due to their exaggerated properties, such as huge size, long chemical bond, large polarization and electric dipole moment, abundant vibrational states and exotic adiabatic potentials. The binding mechanism of Rydberg molecules is a low-energy scattering interaction between the Rydberg electron and the ground state atom for ground-Rydberg molecules or long-range multipole interaction for Rydberg-atom macrodimers and Rydberg-ion molecules, in contrast to covalent bonds, ionic bonds of normal and van der Waals interaction. Owing to its huge size, the dynamic evolution becomes slow compared with normal diatomic molecules and the ultra-long chemical bonds allow being imaged directly by high resolution imaging technology, which makes it convenient to observe the molecular dynamics process chemical reaction process in real time. The investigation of Rydberg molecules will be significant for understanding the mechanism of molecular collision and quantum chemical reaction. In this work, we study the ultra-cold Rydberg-ground state molecules theoretically and experimentally. Theoretically, we calculate the adiabatic potential energy curve of cesium (36D 5/2+ 6S 1/2) Rydberg molecule based on the Fermi model of low energy electron scattering by numerically solving the Hamiltonian of Rydberg molecules. And also, we obtain its characteristic parameters, such as the potential depth, binding energy and equilibrium nuclear distance of Rydberg molecule. Experimentally, the Rydberg-ground molecules are investigated by a photoassociation spectroscopy, where two laser pulses are used to achieve a two-photon transition, and their spectra are obtained by ion detection technology. We successfully observe the Rydberg-ground state molecular spectra that correspond to a scattering triplet and a scattering single-triplet mixture ( S,TΣ). The measured binding energy of Rydberg-ground state molecules is in good agreement with the theoretical result. In addition, taking the Rydberg-ground state molecules formed by scattering triplet ( TΣ) for example, we demonstrate the spectrum broadening of Rydberg molecules in a weak electric field, from which we obtain the permanent electric dipole moments $|\bar{d}|$ of polar Rydberg-ground state molecules about (12.10$ \pm $ 1.65) Debye ((4.76$ \pm $ 0.65) ea 0). The results are consistent with the theoretical calculations. Our study provides a feasible scheme for the experimental preparation of D-type Rydberg-ground molecules, which is of great significance in studying the binding mechanism and the spectral characteristics of polar Rydberg molecules.-
Keywords:
- ultra-cold Rydberg-ground molecule/
- photoassociation spectrum/
- adiabatic potential energy curve/
- permanent electric dipole moment
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