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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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  • by condition-label-red ( 657497 ) on Thursday August 25, 2011 @04:02PM (#37211334) Homepage
    Did anyone else notice that the article with the images has an incorrect definition of imaginary numbers (i.e. says i=sqrt(1) instead of i=sqrt(-1) ).
  • by Anonymous Coward

    These methods do not image orbitals themselves - it is generally regarded as impossible to do this. These instead image electron density, which is separate but related (square of the wavefunction)

    • True, but the shape of the isodensity surface is so closely related (the square of the wave function) that imaging one can pretty much validate the other. Also, while in the journal article they show the MO, the actual comparison between the image and MO theory is on the basis of electron density.

    • by scheme ( 19778 )

      According to the article, they actually do image the orbitals because they're looking at the interaction of the orbitals of CO and the target orbitals. This way they can calculate phase information and get the actual orbitals themselves instead of just electron density.

  • Does that mean there's some slight difference from the theoretical model or just an artifact of how the cloud was imaged?

    • Looks like I am the only one who is not impressed by the comparison pictures. Pictures basically match in "shape", but not exactly in density distribution.

      It seems to me that it's not very difficult to figure out the shape, that is where the minimums and maximums are without any computations.

  • The same group of researchers published a paper in 2009 in the journal Science using a technique called atomic force microscopy (AFM) rather than the scanning tunneling microscopy (STM) approached used here. This technique allowed them to resolve the atomic structure of pentacene, showing the classic ring structure as one might see drawn on a chalk board in their chemistry class. Combined with their means of imaging molecular orbitals by STM, these researchers have developed some really nice tools for stu

  • I remember having seen this very same picture a year ago or so posted here... It's still in my pictures folder because it really impressed me that time. Guess it shows that chemistry isn't alchemy after all. Link to the original article []
    • My mistake. As always, I didn't RTFA before posting. Now I realize that they're talking about the molecuar orbitals (who would've guessed!) and not the picture taken by IBM before. It's actually pretty nice. Again, apologies.
  • Of course some differences between theory and practice can be expected. For example, some experimental noise is expected. And at these scales, some fuzziness is also weird if it wouldn't happen.

    However the topology should be correct. Now in the top image on the right there is a "white" area at the top. Whereas on the left (the real data) the white area at the top has a dent in it. As if there is a black area on the top with two white areas on the corners.

    In short: From this experiment I'd say: The theoretic

    • by cnettel ( 836611 )
      I think there is a dent even in the simulated one. Remember that these 2D visualizations are only representations of the 3D densities. Where you put your cutoff for surfaces, or in this case, where you put the steepest slope in your grayscale definition, can influence the perceived shape a lot more than what is actually the case.
  • The square root of -1?
  • Science : it works, bitches.

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