Ovcharenko, Y.LaForge, A. C.Langbehn, B.Plekan, O.Cucini, R.Finetti, P.O’Keeffe, P.Iablonskyi, D.Nishiyama, T.Ueda, K.Piseri, P.Di Fraia, M.Richter, R.Coreno, M.Callegari, C.Prince, K. C.Stienkemeier, F.Möller, T.Mudrich, M.2022-02-172022-02-172020-08-17https://depositonce.tu-berlin.de/handle/11303/16439http://dx.doi.org/10.14279/depositonce-15215The ionization dynamics of helium droplets irradiated by intense, femtosecond extreme ultraviolet (XUV) pulses is investigated in detail by photoelectron spectroscopy. Helium droplets are resonantly excited to atomic-like 2p states with a photon energy of 21.5 eV and autoionize by interatomic Coulombic decay (ICD). A complex evolution of the electron spectra as a function of droplet size (250 to 106 He atoms per droplet) and XUV intensity (109–1012 W cm−2) is observed, ranging from narrow atomic-like peaks that are due to binary autoionization, to an unstructured feature characteristic of electron emission from a nanoplasma. The experimental results are analyzed and interpreted with the help of a numerical simulation based on rate equations taking into account all relevant processes—multi-step ionization, electronic relaxation, ICD, secondary inelastic collisions, desorption of electronically excited atoms, and collective autoionization (CAI).en530 PhysikHe nanodropletsinteratomic Coulombic decaycollective autoionizationnanoplasmaArticle2022-02-111367-2630