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Issue 32, 2011
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Bias-controlled selective excitation of vibrational modes in molecular junctions: a route towards mode-selective chemistry

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Abstract

We show that individual vibrational modes in single-molecule junctions with asymmetric molecule–lead coupling can be selectively excited by applying an external bias voltage. Thereby, a non-statistical distribution of vibrational energy can be generated, that is, a mode with a higher frequency can be stronger excited than a mode with a lower frequency. This is of particular interest in the context of mode-selective chemistry, where one aims to break specific (not necessarily the weakest) chemical bond in a molecule. Such mode-selective vibrational excitation is demonstrated for two generic model systems representing asymmetric molecular junctions and/or scanning tunneling microscopy experiments. To this end, we employ two complementary theoretical approaches, a nonequilibrium Green's function approach and a master equation approach. The comparison of both methods reveals good agreement in describing resonant electron transport through a single-molecule contact, where differences between the approaches highlight the role of non-resonant transport processes, in particular co-tunneling and off-resonant electron–hole pair creation processes.

Graphical abstract: Bias-controlled selective excitation of vibrational modes in molecular junctions: a route towards mode-selective chemistry

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Publication details

The article was received on 13 Apr 2011, accepted on 31 May 2011 and first published on 20 Jul 2011


Article type: Paper
DOI: 10.1039/C1CP21161G
Citation: Phys. Chem. Chem. Phys., 2011,13, 14333-14349
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    Bias-controlled selective excitation of vibrational modes in molecular junctions: a route towards mode-selective chemistry

    R. Volkovich, R. Härtle, M. Thoss and U. Peskin, Phys. Chem. Chem. Phys., 2011, 13, 14333
    DOI: 10.1039/C1CP21161G

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