论文标题
两光子高于氦的阈值电离
Two-photon Above Threshold Ionization of Helium
论文作者
论文摘要
多光子电离为氦原子中电子相关性的性质提供了一个清晰的窗口。在本研究中，最终的状态能量范围延伸至$ n = 2 $和$ n = 3 $电离阈值附近的区域，在该区域中，两光子电离通过在最低阈值以上的连续中间状态下进行。我们的计算是使用多通道量子缺陷理论（MQDT）和简化的R-Matrix方法进行的。使用Robicheaux和Gao开发的不均匀R-Matrix方法评估了两光子电离振幅中所有中间状态的总和和集成。该方法与MQDT的无缝连接使我们能够呈现最终状态Rydberg共振的高分辨率光谱。我们的分析将共鸣归类于$ n = 2 $阈值的群体理论量子数。发现它们的主要衰变通道可以遵守这些偶数偶然性状态的先前猜测倾向规则，而不是与单个光子电离有关的奇数状态所观察到的。
Multiphoton ionization provides a clear window into the nature of electron correlations in the helium atom. In the present study, the final state energy range extends up to the region near the $N=2$ and $N=3$ ionization thresholds, where two-photon ionization proceeds via continuum intermediate states above the lowest threshold. Our calculations are performed using multichannel quantum defect theory (MQDT) and the streamlined R-matrix method. The sum and integration over all intermediate states in the two-photon ionization amplitude is evaluated using the inhomogeneous R-matrix method developed by Robicheaux and Gao. The seamless connection of that method with MQDT allows us to present high resolution spectra of the final state Rydberg resonances. Our analysis classifies the resonances above the $N=2$ threshold in terms of their group theory quantum numbers. Their dominant decay channels are found to obey the previously conjectured propensity rule far more weakly for these even parity states than was observed for the odd-parity states relevant to single photon ionization.
