The interaction of chemical functional groups with their environment determines many chemical and physical processes, and can be revealed by the dephasing of the vibrational coherence.  To investigate this process with interface specificity, we use Free Induction Decay-Sum-Frequency Generation (FID-SFG) in which a short infrared pulse coherently excites vibrational oscillators and, after a controlled time delay, a second pulse up-converts the macroscopic polarization associated with excited oscillators, generating a field at the sum frequency.  Monitoring the SFG response as a function of the delay between the IR pulse and the upconverting pulse provides information about the dephasing process with interface specificity; SFG is forbidden in non-centrosymmetric environments.  As dephasing typically occurs on an ultrashort time-scale, we developed an FID-SFG experimental setup capable of temporally resolving vibrational dynamics at interfaces with sub-50 femtosecond time resolution.  We will report the FID-SFG dynamics of free OH stretch vibrational mode at the solid-aqueous interfaces.

Vibrational dynamics of interfacial water by free induction decay sum-frequency generation (FID-SFG)

244th National Meeting (2012)

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