2018, Cirelli, Claudio, Marante, Carlos, Heuser, Sebastian, Petersson, C.L.M., Galán, Álvaro Jiménez, Argenti, Luca, Zhong, Shiyang, Busto, David, Isinger, Marcus, Nandi, Saikat, Maclot, Sylvain, Rading, Linnea, Johnsson, Per, Gisselbrecht, Mathieu, Lucchini, Matteo, Gallmann, Lukas, Dahlström, J. Marcus, Lindroth, Eva, L’Huillier, Anne, Martín, Fernando, Keller, Ursula

Electron correlation and multielectron effects are fundamental interactions that govern many physical and chemical processes in atomic, molecular and solid state systems. The process of autoionization, induced by resonant excitation of electrons into discrete states present in the spectral continuum of atomic and molecular targets, is mediated by electron correlation. Here we investigate the attosecond photoemission dynamics in argon in the 20-40 eV spectral range, in the vicinity of the 3s -1 np autoionizing resonances. We present measurements of the differential photoionization cross section and extract energy and angle-dependent atomic time delays with an attosecond interferometric method. With the support of a theoretical model, we are able to attribute a large part of the measured time delay anisotropy to the presence of autoionizing resonances, which not only distort the phase of the emitted photoelectron wave packet but also introduce an angular dependence.

2020, Malm, Erik, Wikmark, Hampus, Pfau, Bastian, Villanueva-Perez, Pablo, Rudawski, Piotr, Peschel, Jasper, Maclot, Sylvain, Schneider, Michael, Eisebitt, Stefan, Mikkelsen, Anders, L’Huillier, Anne, Johnsson, Per

Singleshot polychromatic coherent diffractive imaging is performed with a high-intensity high-order harmonic generation source. The coherence properties are analyzed and several reconstructions show the shot-to-shot fluctuations of the incident beam wavefront. The method is based on a multi-step approach. First, the spectrum is extracted from double-slit diffraction data. The spectrum is used as input to extract the monochromatic sample diffraction pattern, then phase retrieval is performed on the quasi-monochromatic data to obtain the sample’s exit surface wave. Reconstructions based on guided error reduction (ER) and alternating direction method of multipliers (ADMM) are compared. ADMM allows additional penalty terms to be included in the cost functional to promote sparsity within the reconstruction. © 2020 Optical Society of America under the terms of the OSA Open Access Publishing Agreement.