中关村论坛第268期

日期：2015.3.20

原标题：Surface Femtochemistry: the Coupling of Electron and Nuclear Motion at Adsorbate Covered Solid Surfaces

　　报告人简介：

　　Prof. Hrvoje Petek received his PhD in chemistry from the University of California, Berkeley (United States) in 1985, and then he became a postdoctoral fellow in Prof. Yoshihara’s group at Institute for Molecular Science in Japan. From 1987, he became a Research Associate in the same institute. Starting from 1993, he worked as a Senior Research Scientist and group leader in Hitachi Advanced Research Laboratory in Japan. In 2000, he started his new career as a Full Professor both in Physics and Chemistry at the University of Pittsburgh. He was the co-Director of Peterson Institute for Nanoscience and Engineering in the University from 2005 to 2012. In 2014, he was appointed as the Richard King Mellon Chair Professor of Physics and Astronomy, the most prestigious professor Chair at the University. Currently he is also a member of the National Research and Development Agency Committee of Japan. Professor Hrvoje Petek has been awarded many research prizes from different International Academic Institutes Organizations. From 2006, he has been the Editor-in-Chief of Progress in Surface Science.

　　报告摘要:

　　Photoexcitation of a surface can induce electron transfer from the occupied bands of metal or semiconductor to the unoccupied electronic states of adsorbed molecules. Recording of two-photon photoemission spectra, which is initiated by such electron transfer transition, identifies the unoccupied molecular states that can trigger surface femtochemistry. The sudden change in the electron distribution of a molecule upon electronic transition turns on chemical forces, which induce nuclear motion on an excited state potential surface if electronic relaxation processes are sufficiently slow for the nuclear motion to evolve. The nuclear motion in turn stabilizes the excited state, which can be detected through changes in the 2PP spectra as a delay between the excitation and photoemission laser pulses is scanned on the femtosecond time scale. I will present several examples from the simple atomic case of the frustrated desorption alkali atoms from noble metals[1], to proton-coupled electron transfer instigated by wet electrons[2] on methanol covered TiO2 surfaces[3].

　　[1] Petek, H., Weida, M.J., Nagano, H., & Ogawa, S., Real-time observation of atomic motion above a metal surface. Science 288, 1402-1404 (2000).

　　[2] Onda, K. et al., Wet Electrons at the H2O/TiO2(110) Surface. Science 308, 1154-1158 (2005).

　　[3] Li, B. et al., Ultrafast interfacial proton-coupled electron transfer. Science 311, 1436-1440 (2006).