Abstract. Two-photon photoemission spectroscopy is employed to analyze reversible changes in the electronic structure of the molecular switch tetra-tert-butyl-azobenzene (TBA) adsorbed on Au(111) induced by UV-light and thermal activation. Cycles of illumination and annealing steps have confirmed the reversibility of the switching process, which we assign to a trans/cis -isomerization of TBA molecules in direct contact with the Au(111) surface. Pronounced changes in the photoelectron spectra due to UV-light exposure allow to calculate an effective cross section of σeff ≈ 4 ∙ 10-22 cm-2 at 4.14 eV and σeff ≈ 6 ∙ 10-21 cm-2 at 4.4 eV for the trans to cis -isomerization, respectively.
The publication is available at link DOI:10.1016/j.cplett.2007.07.005