title: A single molecule view of bistilbene photoisomerization on a surface using scanning tunneling microscopy.
abstract: The advent of scanning tunneling microscopy (STM) has permitted a detailed atomic view of organic molecules adsorbed on solid surfaces. In this work, we make use of the STM to provide an unprecedented direct single-molecule perspective on the cis-trans photoisomerization of stilbene molecules within ordered monolayers physisorbed on the Ag/Ge(111)-( radical3x radical3)R30 degrees surface. The STM view of the molecular structure transformation upon irradiation provides direct evidence for the generally accepted one-bond-flip mechanism proposed for the photoisomerization process. We also find that the surface environment produces a profound effect on the reaction mechanism. The reaction is observed to proceed mainly through pairs of co-isomerizing molecules situated at domain boundaries. To explain these observations, we propose a mechanism whereby excitation migrates to the domain boundary and the reaction occurs through a biexciton reaction pathway.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, P.O. Box 23-166, Taipei 106, Taiwan.
authors.forename: Chih-Song
authors.initials: CS
authors.lastname: Tsai
authors.forename: Juen-Kai
authors.initials: JK
authors.lastname: Wang
authors.forename: Rex T
authors.initials: RT
authors.lastname: Skodje
authors.forename: Jiing-Chyuan
authors.initials: JC
authors.lastname: Lin