Tracking Surface Shakes

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Science  15 Feb 2008:
Vol. 319, Issue 5865, pp. 879
DOI: 10.1126/science.319.5865.879a

Two-dimensional infrared (2D-IR) spectroscopy has recently proven useful for tracking chemical dynamics through shifts in detected molecular vibrations. The “2D” refers not to a spatial framework but rather to the initial and final sets of mode populations that are simultaneously monitored at different vibrational frequencies. Bredenbeck et al. extend this technique to achieve surface specificity by combining it with sum frequency generation (SFG). This latter, well-established class of spectroscopy affords a background-free signal arising from the additive mixing of two different frequencies of light at an interface—a process that fails to build intensity in a bulk 3D environment where the polarizations of stacked molecular layers cancel one another out. The authors applied their SFG 2D-IR hybrid to the characterization of vibrational energy flow in the hydrophobic alkyl tails protruding from a water-dodecanol interface. — JSY

J. Am. Chem. Soc. 130, 10.1021/ja710099c (2008).

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