SurfaceScience21 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 63: Poster Session V: Electron-driven processes at surfaces and interfaces
O 63.5: Poster
Mittwoch, 3. März 2021, 10:30–12:30, P
Transient reflectivity in nonequilibrium warm dense gold — •Pascal D. Ndione1, Sebastian T. Weber1, Dirk O. Gericke2, and Baerbel Rethfeld1 — 1Department of Physics and OPTIMAS Research Center, Technische Universität Kaiserslautern — 2CFSA, Department of Physics, University of Warwick
Ultrashort and intense laser pulses can induce strong modification of materials properties such as optical parameters determining the amount of absorbed energy in time. After excitation with lasers of high energy, the electrons thermalize fast to a hot Fermi distribution. Yet, the band occupation numbers are still in strong nonequilibrium as particle exchange between the bands takes longer than energy exchange.
We study excitation of gold with optical photons. Only the 5d and 6sp bands are considered to be active. We present a density-resolved approach coupled with a two-temperature model to follow the nonequilibrium band occupation. A Drude-Lorentz formalism is used to calculate the dielectric function of the heated system. We simulate the temporal evolution of a probe reflectivity up to delay time of 6 ps. Our predictions reveal over time a strong compensation of damping mechanisms for the electrons and phonons. The good agreement between simulation and time-resolved measurements suggests a good understanding of the experimental data and the underlying physical processes, which has been interpreted differently as a lack of dynamics on the subpicosecond timescale.