Erlangen 2022 – scientific programme

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MO: Fachverband Molekülphysik

MO 2: X-ray FELs (joint session MO/A)

MO 2.8: Talk

Monday, March 14, 2022, 15:45–16:00, MO-H5

Competition of interatomic Coulombic decay and autoionization in doubly excited helium nanodroplets — •Björn Bastian, Jakob D. Asmussen, Ltaief B. Ltaief, Akgash Sundaralingam, Catharina I. Vandekerckhove, and Marcel Mudrich — Department of Physics and Astronomy, Aarhus University, DK

Double-excitation states in helium atoms are an important model system to study electron-electron correlation. Doubly excited atoms can autoionize and the interference with the direct ionization pathway gives rise to characteristic Fano peaks in the photoexcitation spectrum [1] which has also been observed in helium nanodroplets [2]. In dimers or clusters, the de-excitation energy can instead be transferred and cause ionization of the environment. Theory has shown, that this interatomic Coulombic decay (ICD) pathway becomes fast at small interatomic distances and competes with autoionization especially in large environments [3].

We present photoion-photoelectron coincidence spectra around the Fano resonance below the N=2 ionization threshold in helium nanodroplets that have been recorded at our new endstation at the AMOLine of the ASTRID2 synchrotron at Aarhus. Slow electrons reveal ICD or secondary inelastic scattering. Highly resolved electron spectra recorded at various photon energies across the Fano resonance reveal the details of the decay process.

[1] Domke et al. Phys. Rev. Lett. 66, 1306 (1991). [2] LaForge et al. Phys. Rev. A 93, 050502 (2016). [3] Jabbari et al. Chem. Phys. Lett. 754, 137571 (2020).