Stark效应是原子和分子在外电场中能级的分裂和移动及电离能降低的现象。理论预言外电场中原子电离阈值之上（阈上）的能态是存在的。我们已经采用共振多光子电离方法获得了分辨率不好的来自阈上能级的光谱。目前还没有外电场中阈上能级结构的详细实验报道。零动能光谱是最近发展起来的研究电离阈上能级的高分辨率光谱技术，主要应用于无外加电场时分子离子基态和激发态的振动和转动能级研究。本项目拟采用零动能光谱技术研究外电场中铯原子阈上能态信息，实验上获得阈上态的高分辨率光谱、能级结构、跃迁几率、寿命、能级交叉与反交叉、偶极矩和极化率等重要特性参数。同时进行理论计算，通过数值求解外场中的薛定谔方程获得阈上态的波函数、跃迁几率、电荷分布、电偶极矩和极化率等特性数据。 本项目将开启原子分子外电场中阈上能态特性的研究之门, 也为零动能光谱学开辟一个新的应用领域。

The Stark effect is the phenomenon of energy-levels splitting and moving, and ionization energy lowering for the atoms and molecules in an external electric field.The theory predicts that the states above ionization threshold exist in an external electric field. We have used the resonance multi-photon ionization method to obtain the low-resolution spectra come from the levels above ionization threshold. At present there is no detailed experimental reports about these levels. Zero kinetic energy (ZEKE) spectroscopy is recently developed a high-resolution spectroscopy, which is mainly used to study the vibrational and rotational levels of the molecular ion ground state and excited states under the condition of no external electric field. In this project we intend to use the the ZEKE spectroscopy to study the states above the threshold of the atomic cesium in an field. We shall experimentally observe and obtain the high-resolution spectra, energy-level structure, transition probability, life time, levels cross-over and anti cross-over, electric dipole moment, and polarizability for states above the threshold in Stark effect. The theoretical work will be performed meantime. The characteristic data of the states above the threshold, such as wave function, transition probability, charge distribution, electric dipole moment, polarizability, and so on, are to be computed by numerically solving the Schrodinger equation with an electric field. This project will not only open the door of studying atomic and molecular states above the threshold in Stark effect but also make a new application aera of ZEKE spectroscopy.