Straub Michael, Ding Thomas, Rebholz Marc, Borisova Gergana D, Magunia Alexander, Lindenblatt Hannes, Meister Severin, Trost Florian, Wang Yimeng, Palutke Steffen, Braune Markus, Düsterer Stefan, Treusch Rolf, Greene Chris H, Moshammer Robert, Pfeifer Thomas, Ott Christian
Max-Planck-Institut für Kernphysik, Saupfercheckweg 1, D-69117 Heidelberg, Germany.
Department of Physics and Astronomy, Purdue University, West Lafayette, Indiana 47907, USA.
Phys Rev Lett. 2022 Oct 28;129(18):183204. doi: 10.1103/PhysRevLett.129.183204.
We report the measurement of the photoelectron angular distribution of two-photon single-ionization near the 2p^{2} ^{1}D^{e} double-excitation resonance in helium, benchmarking the fundamental nonlinear interaction of two photons with two correlated electrons. This observation is enabled by the unique combination of intense extreme ultraviolet pulses, delivered at the high-repetition-rate free-electron laser in Hamburg (FLASH), ionizing a jet of cryogenically cooled helium atoms in a reaction microscope. The spectral structure of the intense self-amplified spontaneous emission free-electron laser pulses has been resolved on a single-shot level to allow for post selection of pulses, leading to an enhanced spectral resolution, and introducing a new experimental method. The measured angular distribution is directly compared to state-of-the-art theory based on multichannel quantum defect theory and the streamlined R-matrix method. These results and experimental methodology open a promising route for exploring fundamental interactions of few photons with few electrons in general.
我们报告了在氦气中 2p²¹D⁰ 双激发共振附近双光子单电离的光电子角分布测量结果，以此为两个光子与两个相关电子的基本非线性相互作用提供基准。这一观测得以实现，得益于高强度极紫外脉冲的独特组合，这些脉冲由汉堡的高重复率自由电子激光（FLASH）产生，在反应显微镜中使低温冷却的氦原子射流发生电离。强自放大自发辐射自由电子激光脉冲的光谱结构已在单次测量水平上得到解析，从而能够对脉冲进行后选择，提高了光谱分辨率，并引入了一种新的实验方法。所测量的角分布与基于多通道量子亏损理论和简化 R 矩阵方法的最新理论直接进行了比较。这些结果和实验方法总体上为探索少数光子与少数电子的基本相互作用开辟了一条充满希望的途径。
