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United Kingdom Science

Imaging the Molecular Orbitals of Pentacene 70

eparker05 writes "Researchers at University of Liverpool have used a scanning tunneling microscope to image the aromatic molecule pentacene (Abstract). Not unexpectedly, the resulting images showed an astonishingly close correlation to the theoretically predicted molecular orbitals. This incredible set of images reminds me of the group that imaged a single carbon atom in 2009."
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Imaging the Molecular Orbitals of Pentacene

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  • Re:Old hat (Score:5, Informative)

    by TeethWhitener ( 1625259 ) on Thursday August 25, 2011 @06:39PM (#37213288)

    The only thing that is new about this article is a slightly different flavor of STM

    Now that's just plain wrong. First off, the pentacene molecule imaged by the group at IBM was imaged using atomic force microscopy (AFM), which uses a nanoscale piezoelectric cantilever to measure the force between the tip of the microscope and the substrate. The IBM team realized that picking up a single CO molecule with the tip allowed them to have an atomically sharp tip, thus giving them the drastically increased resolution apparent in that paper. This paper presents an STM method, which uses the current caused by electron tunneling between a tip and substrate (which dies off exponentially with distance between the two). The major breakthrough is this: scientists working in this field have known for quite some time that the electron tunneling was a function of both the starting state (tip state) and the ending state (substrate) of the electron. The problem with this is that the tip state up until now has only been known very vaguely. At the atomic level, the tip of the STM is in general a poorly defined blob of metal. What the researchers in this paper have done is pick up a CO molecule to act as the tip of the probe, just like the researchers on the pentacene paper before. The advantage now is that we can model CO quite well quantum mechanically, so that we have a much better idea of the starting state of the electrons. Of course, there will be some interaction of the CO with the metal in the tip, but nonetheless, this method provides us with a much clearer picture of what the electrons are actually doing when they tunnel from the tip to the substrate below. This is the reason that the researchers were able to get so much more information out of these experiments than previous researchers. /rant

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