Berlin 2018 – scientific programme
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O: Fachverband Oberflächenphysik
O 57: Electronic structure of surfaces: Spectroscopy, surface states II
O 57.5: Talk
Wednesday, March 14, 2018, 11:45–12:00, MA 042
Correction and Suppression of the Space-Charge Effect in Cathode-Lens Microscopes — •Benedikt Schönhense1, Katerina Medjanik2, Dmitry Vasilyev2, Sergey Babenkov2, Martin Ellguth2, Hans-Joachim Elmers2, and Gerd Schönhense2 — 1Imperial College London, UK — 2JGU, Inst. für Physik, Mainz, Germany
Previous pump-and-probe photoemission experiments have revealed that the Coulomb interaction in the pulsed beam (commonly referred to as "space-charge problem") is a serious obstacle, in particular due to background electrons released by the pump pulse [1]. Theoretical work [2] has uncovered the reason for the dramatic deterioration of the imaging performance in conventional cathode lenses (PEEMs, k-microscopes): All slow electrons are efficiently focused into the lens column where they travel along the optical axis and exert strong forces on the primary photoelectrons. Shifts up to 10 eV have been measured at the conditions of beamline P04 of PETRA III. We present strategies of an a-posteriori correction of the Lorentzian deformation of the momentum distributions [2] and of an a-priori suppression of the deterministic part of Coulomb interaction by "extraction-field tailoring".
[1] L.-P. Oloff et al., J. of Appl. Phys. 119, 225106 (2016)
[2] B. Schönhense et al., New J. Phys., under review