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O: Fachverband Oberflächenphysik

O 5: Dynamics of Molecules on Surfaces

O 5.5: Talk

Monday, March 7, 2016, 11:30–11:45, S053

Vibrationally induced hydrogen-atom transfer in a single porphycene molecule on Cu(110) — •Shuyi Liu¹, Delroy Baugh¹, Xunhua Zhao¹, Sylwester Gawinkowski², Jacek Waluk², and Takashi Kumagai¹ — ¹Fritz-Haber Institute, Berlin, Germany — ²Polish Academy of Sciences, Warsaw, Poland

In this talk we present results on the tautomerization of a single porphycene molecules on Cu(110) induced by vibrational excitation via inelastic electron tunneling using an STM. The cis-cis tautomerization was investigated by STS and STM Action Spectroscopy (STM-AS) [1]. STM-AS spectra show steep increases at certain bias voltages, and also exhibits a clear isotope effect when deuterium is substituted for the transferring H-atoms, revealing a vibrationally mediated process. These results indicate excitation of skeletal motion of porphycene plays a crucial role in the reaction. DFT calculations suggest the excited skeletal vibrational mode and N-H(D) stretching transfers energy to the reaction coordinate mode(s) via the anharmonic couplings within the molecule. We also found that the N-H stretching vibration exhibits a noticeable broadening which may be rationalized by strong the anharmonicity of the mode potential that results from the H-bond. Our approach provides a microscopic insight into the electron-vibrational coupling within a single molecule and how it can trigger a chemical reaction. [1] T.K. Prog. Surf. Sci. 90, 239 (2015).