Dresden 2020 – scientific programme

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O: Fachverband Oberflächenphysik

O 48: Poster Session - Electronic Structure of Surfaces: Spectroscopy, Surface States

O 48.5: Poster

Tuesday, March 17, 2020, 18:15–20:00, P2/EG

Towards ultrafast time-resolved orbital imaging using a ToF-based momentum microscope and photoelectrons extracted by HHG light — •Wiebke Bennecke, Matthijs Jansen, Sabine Steil, Marius Keunecke, David Schmitt, Marten Düvel, Christina Möller, Daniel Steil, and Stefan Mathias — I. Physikalisches Institut, Georg-August-Universität Göttingen

Orbital imaging (OI) is a powerful method to visualize molecular orbitals in molecules-metal interfaces using angle-resolved photoemission spectroscopy (ARPES) data and phase retrieval algorithms [Puschnig et al., Science 326, 702-706 (2009)]. On this poster, we will report on our progress towards a demonstration of time-resolved imaging of optically excited orbitals. OI requires the precise preparation of a few highly ordered monolayers of molecules on a monocrystalline metallic substrate. We achieve this by thermal evaporation from a Knudsen cell in combination with LEED and UV photoemission measurements to verify the sample quality. Our photoemission setup consists of a momentum microscope and a high harmonic generation beamline at 26.5 eV, which yields the full momentum- and energy-dependent photoelectron spectrum of the absorbed molecules in a single measurement. We combine this setup with UV, visible and IR pump beamlines, which allows us to induce a wide range of optical excitations on a femtosecond time scale. The measured time-resolved photoelectron spectra are analysed using a sparsity-driven phase retrieval algorithm, which enables us to visualize the molecular orbitals in real space while requiring only limited prior knowledge of the molecular orbital.