TY  - JOUR
A1  - Kühn, Danilo
A1  - Giangrisostomi, Erika
A1  - Jay, Raphael Martin
A1  - Sorgenfrei, Florian
A1  - Föhlisch, Alexander
T1  - The influence of x-ray pulse length on space-charge effects in optical pump/x-ray probe photoemission
JF  - New journal of physics : the open-access journal for physics
N2  - Pump-probe photoelectron spectroscopy (PES) is a versatile tool to investigate the dynamics of transient states of excited matter. Vacuum space-charge effects can mask these dynamics and complicate the interpretation of electron spectra. Here we report on space-charge effects in Au 4f photoemission from a polycrystalline gold surface, excited with moderately intense 90 ps (FWHM) soft x-ray probe pulses, under the influence of the Coulomb forces exerted by a pump electron cloud, which was produced by intense 40 fs laser pulses. The experimentally observed kinetic energy shift and spectral broadening of the Au 4f lines, measured with highly-efficient time-of-flight spectroscopy, are in good agreement with simulations utilizing a mean-field model of the electrostatic pump electron potential. This confirms that the line broadening is predominantly caused by variations in the take-off time of the probe electrons without appreciable influence of local scattering events. Our findings might be of general interest for pump-probe PES with picosecond-pulse-length sources.
KW  - space-charge effects
KW  - mean-field model
KW  - x-ray photoemission
KW  - electron spectroscopy
KW  - pump-probe
KW  - ARTOF
Y1  - 2019
U6  - https://doi.org/10.1088/1367-2630/ab2f5c
SN  - 1367-2630
VL  - 21
PB  - IOP Publ. Ltd.
CY  - Bristol
ER  -