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Science 15 October 2004:
Vol. 306. no. 5695, p. 369
DOI: 10.1126/science.306.5695.369n
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If energy is put into a specific molecular vibration, such as through laser excitation, it tends to spread out rapidly to neighboring bonds and molecules and eventually ends up as heat. The specifics of this dissipation process can be fairly complicated at interfaces and in solution. Deàk et al. (p. 473, published online 23 September 2004) studied energy flow through reverse micelles, which are pockets of water suspended by surfactants in a nonpolar liquid. By exciting water vibrations with infrared radiation and using a picosecond time-resolved Raman probe technique, they assembled a highly detailed, frame-by-frame sequence of energy transfer steps from the water through the surfactant layer and into the carbon tetrachloride solvent. The technique was sensitive enough to distinguish vibrations in the polar surfactant head groups from those in the nonpolar tails. Surprisingly, energy transfer to the solvent was faster from the head groups than from the closer tails.




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