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- ItemAttosecond electron thermalization in laser-induced nonsequential multiple ionization: Hard versus glancing collisions(College Park, MD : Institute of Physics Publishing, 2008) Liu, X.; De Morisson Faria, C.F.; Becker, W.A recollision-based largely classical statistical model of laser-induced nonsequential multiple (N-fold) ionization of atoms is further explored. Upon its return to the ionic core, the first-ionized electron interacts with the other N - 1 bound electrons either through a contact or a Coulomb interaction. The returning electron may leave either immediately after this interaction or join the other electrons to form a thermalized complex which leaves the ion after the delay Δt, which is the sum of a thermalization time and a possible additional dwell time. Good agreement with the available triple and quadruple ionization data in neon and argon is obtained with the contact scenario and delays of Δt = 0.17 T and 0.265 T, respectively, with T the laser period. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
- ItemTowards time resolved core level photoelectron spectroscopy with femtosecond x-ray free-electron lasers(College Park, MD : Institute of Physics Publishing, 2008) Pietzsch, A.; Föhlisch, A.; Beye, M.; Deppe, M.; Hennies, F.; Nagasono, M.; Suljotil, E.; Wurth, W.; Gahl, C.; Dörich, K.; Melnikov, A.We have performed core level photoelectron spectroscopy on a W(110) single crystal with femtosecond XUV pulses from the free-electron laser at Hamburg (FLASH). We demonstrate experimentally and through theoretical modelling that for a suitable range of photon fluences per pulse, time-resolved photoemission experiments on solid surfaces are possible. Using FLASH pulses in combination with a synchronized optical laser, we have performed femtosecond time-resolved core-level photoelectron spectroscopy and observed sideband formation on the W 4f lines indicating a cross correlation between femtosecond optical and XUV pulses. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.
- ItemInterference in strong-field ionization of a two-centre atomic system(College Park, MD : Institute of Physics Publishing, 2008) Ansari, Z.; Böttcher, M.; Manschwetus, B.; Rottke, H.; Sandner, W.; Verhoef, A.; Lezius, M.; Paulus, G.G.; Saenz, A.; Milošević, D.B.Strong-field photoionization of argon dimers by a few-cycle laser pulse is investigated using electron-ion coincidence momentum spectroscopy. The momentum distribution of the photoelectrons exhibits interference due to the emission from the two atomic argon centres, in analogy with a Young's doubleslit experiment. However, a simulation of the dimer photoelectron momentum spectrum based on the atomic spectrum supplemented with a theoretically derived interference term leads to distinct deviations from the experimental result. The deviations may have their origin in a complex electron dynamics during strong-field ionization of the Ar2 dimer. © IOP Publishing Ltd and Deutsche Physikalische Gesellschaft.