Skip to comments.Two techniques unite to provide molecular detail
Posted on 06/06/2013 6:51:44 PM PDT by neverdem
Raman spectroscopy souped up with scanning tunnelling microscopy hones in on individual atoms and bonds.
Prepare to take flight across the surface of a molecule. An unprecedented window on the nanoscale world lets you feel the heft of the atoms beneath and test the strength of the chemical bonds that hold them together.
This vision is now a reality, thanks to a system reported in this week's Nature1 that combines the best features of two imaging techniques: Raman spectroscopy and the scanning tunnelling microscope (STM). It enables you to look at the guts of a molecule, says Joanna Atkin, a spectroscopist at the University of Colorado Boulder, who co-wrote a News and Views commentary to accompany the work2.
Raman spectroscopy uses laser light to make sample molecules vibrate in various ways: atoms wag or twist, for example, and chemical bonds stretch back and forth. The photons that make the molecule dance lose a certain amount of energy depending on the movement, and have a lower frequency when they scatter away. Different groups of atoms vibrate in unique ways, so the changes in the scattered light constitute a characteristic fingerprint that can identify a molecule.
But the technique is no good for studying very small samples. Only one in a million photons drives one of these vibrational modes and gets shifted, explains Atkin. The conventional Raman signal from a single molecule would be much too weak to discern.
In recent years, however, researchers have found ways to use Raman spectroscopy on ever-smaller targets, with the help of the incredibly sharp metal tip of an STM. When the tip hovers less than one nanometre above a surface, electrons can quantum-tunnel across the gap; the intensity of the resulting electric current depends on the position and character of the atoms...
(Excerpt) Read more at nature.com ...
Top Left- Raman image
Top Right- Raman with STM
Bottom - Enlarged image with hypothetical molecular arrangement digitally added.
Is any of that correct ?
I think the images come from the scanning tunneling microscopy.
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