We study the excitation and ionization of cesium Rydberg states in an electric field ($\approx 2200\mathrm{V}/\mathrm{cm}$) near the classical field-ionization threshold ($\approx -280{\mathrm{cm}}^{-1}$ binding energy) by three-dimensional (3D) ion-electron coincidence spectroscopy. Cesium atoms are produced by an effusive oven and excited with lasers to Stark-shifted Rydberg states or directly ionized. Using a double time-of-flight setup we record 3D ($X, Y$, time of flight) coincidence imaging of electrons and ions. Above-threshold photoionization creates broad images with poor electron-ion spatial correlation. Fast ionizing states produce very good correlations and the images reveal the electric-field map of the ionization region. Slow ionizing states show that the relatively high atomic velocity is detrimental to the correlations. Experimental data are accurately reproduced by detailed Monte Carlo excitation and ionization simulations based on Stark maps obtained with local-frame transformation (LFT) theory. Agreement between our spectroscopic experiment and LFT theory is very good, with better that hundreds of megahertz accuracy. But, on rare particular states, several gigahertz discrepancy is found. This study can be used to select appropriate states for the creation of ion and electron beams with high brightness, good correlation, and low energy dispersion.

中文翻译：

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通过三维离子电子相关研究铯里德堡态电离：朝向单色电子源

我们研究了电场中铯Rydberg态的激发和电离（$\approx 2200\mathrm{伏特}/\mathrm{厘米}$）接近经典场电离阈值（$\approx -280{\mathrm{厘米}}^{-\mathrm{1个}}$三维（3D）离子电子符合光谱法分析结合能）。铯原子由高能熔炉产生，并用激光激发到斯塔克位移的里德堡态或直接电离。使用双重飞行时间设置，我们记录了3D（$X， ÿ$（飞行时间）电子和离子的重合成像。阈值以上的光电离会创建较差的电子离子空间相关性的宽图像。快速电离态产生非常好的相关性，并且图像揭示了电离区域的电场图。缓慢的电离态表明相对较高的原子速度不利于相关性。通过基于局部帧变换（LFT）理论获得的Stark映射的详细蒙特卡罗激发和电离模拟，可以精确地重现实验数据。我们的光谱实验与LFT理论之间的一致性非常好，精确度高达数百兆赫。但是，在罕见的特定州，发现了几千兆赫的差异。