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A: Fachverband Atomphysik

A 33: Interaction with VUV and X-Ray Light II

A 33.5: Talk

Thursday, March 5, 2009, 18:15–18:30, VMP 8 R208

Double Photoionization of Optically Pumped Lithium Atoms at FLASH — •Ganjun Zhu, Jochen Steinmann, Johannes Albrecht, Michael Schuricke, Alexander Dorn, and Joachim Ullrich — Max-Planck-Institut für Kernphysik, Heidelberg

The combination of intense FEL radiation with modern spectroscopy technique of MOTRIMS (Magneto Optical Trap Recoil Ion Momentum Spectroscopy) will pave the way to numbers of unprecedented experiments in atomic, optical and plasma physics as well as on ultra cold ensembles. For instance, the “multi-electron ejection from light atoms via single-photon absorption" process lies in the very focus of atomic physics, which is the most fundamental few-body reaction.

Here we report on a pilot experiment performed at Flash (FEL LASER at Hamburg), investigating double-photoionization (DPI) phenomena. For the first time, initial target preparation by optical pumping (λ= 671nm , linear polarization) was applied to control the DPI dynamics. It is demonstrated that the Li²⁺ recoil ion momentum distribution changes dramatically as the initial Li(1s²2s) ²S_1/2 ground state is excited to Li(1s²2p) ²P_3/2; and the DPI cross section strongly depends on the spatial alignment of the excited electron wave function. One intuitive interpretation to this new observation could be related with the different overlap of the ionized 1s-electron dipole emission lobes with the aligned 2p-wave function. Thus, the collision probability of both electrons and therefore the DPI cross section differs.