Regensburg 2019 – wissenschaftliches Programm

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O: Fachverband Oberflächenphysik

O 63: Poster Wednesday: Ultrafast Processes

O 63.6: Poster

Mittwoch, 3. April 2019, 17:45–20:00, Poster B1

Oscillating kinetic energy in time-resolved photoemission — •Xinwei Zheng1, Kamil Bobowski1, Dominic Lawrenz1, Robert Carley2, Beatrice Andres1, Cephise Cacho3, Richard Chapman3, Emma Springate3, Serguei Molodtsov2, and Martin Weinelt11Freie Universität Berlin, Fachbereich Physik, Arnimalle 14, 14195 Berlin, Germany — 2European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany — 3Rutherford Appleton Laboratory, Didcot, OX11 0QX, UK

We measured ultrafast time-resolved photoemission spectra on Gd (0001) and W (110) with an IR pump, XUV probe set up at the Artemis laser facility. We observed an oscillating kinetic energy of the photoemitted electrons before time zero. Such oscillations have been observed on the surface state of Gd by Bovensiepen et al. [1]. They described the oscillations with a ponderomotive acceleration of the emitted photoelectrons in a transient grating formed by the interference between the incident and reflected parts of the pump pulse. We performed a further investigation on these oscillations by varying the wavelengths of the pump pulse and found that the amplitude and the phase of the oscillations are pump wavelength-dependent. They show different behavior than predicted by the ponderomotive acceleration model. By comparing the amplitude of the oscillations on different bands, we discovered that the oscillating kinetic energy depends on the initial state of photoemission.

[1] Bovensiepen et al., Phys. Rev. B, 79, 045415 (2009)

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