title: Ultrafast vibrational dynamics at water interfaces.
abstract: Time-resolved sum-frequency vibrational spectroscopy permits the study of hitherto neglected ultrafast vibrational dynamics of neat water interfaces. Measurements on interfacial bonded OH stretch modes revealed relaxation behavior on sub-picosecond time scales in close resemblance to that of bulk water. Vibrational excitation is followed by spectral diffusion, vibrational relaxation, and thermalization in the hydrogen-bonding network. Dephasing of the excitation occurs in </=100 femtoseconds. Population relaxation of the dangling OH stretch was found to have a time constant of 1.3 picoseconds, the same as that for excitation transfer between hydrogen-bonded and unbonded OH stretches of water molecules surrounded by acetone.
authors.affiliation: Department of Physics, University of California, Berkeley, CA 94720, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: McGuire
authors.forename: Y Ron
authors.initials: YR
authors.lastname: Shen