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Calling all Chemistry Experts

  1. Feb 3, 2005 #1
    Daniel Neumark recently attracted attention for his study of negatively-charged water clusters. The clusters are "globs" of water molecules with one extra electron. He found that, for clusters with 50 water molecules, the extra electron was almost always confined to a void in the center of the cluster. For clusters with less than 20 water molecules, the electron was almost always on the surface of the cluster. Over the last 20 years, theorists have speculated as to whether the electron would be inside or outside the cluster, and if both, which case would be favored for small clusters and which would be favored for large clusters. Now the answer is known.

    Using what you now know about the behavior of electrons and wavelengths of radiation, and the space-filling size of water molecules, how might the electronic spectra measured by Prof. Neumark have distinguished the two types of clusters? Justify your answer with calculations, and explain any assumptions.

    Hints and one more question: The spacing between nearest oxygen atoms in ice is about 0.28 nm. Further, the extra electron does not significantly penetrate the space occupied by a water molecule. Suggest the physical reason for why the electron does not penetrate that space.
    Can someone help me with is? I have no clue...
  2. jcsd
  3. Feb 3, 2005 #2


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    You have to make some attempt. Did you try Googling ?
  4. Feb 3, 2005 #3


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    If the electron was on the surface, relatively little energy must be given to excite it, however, if it was in the center, the energy must be higher. The energy can be calculated on the position of the excitation peak.

    The reason why the extra electron cannot penetrate the small space between two oxygen atoms may be due to electronic repulsions, since oxygen has two non-bonding electron pairs, there is a considerable repulsion. A fifth one cannot easily approach to them, I think.
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