Ultrafast dynamics of hydrogen bonds directly observed by time-resolved infrared spectroscopy

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Abstract
Internal, hydrogen bonded OH groups of ethanol oligomers (solvent CCl4) are vibrationally excited by intense picosecond pulses at 3320 cm−1. The transient band shape observed in the OH stretching region (3000 to 3700 cm−1) is monitored by an independently tunable picosecond infrared pulse. The bands in this region are direct probes of hydrogen bridges. The time dependent growth and decay of these bands provides strong evidence for rapid bond breaking with a vibrational predissociation time of ≊5 ps, and for partial reassociation with a time constant of ≊20 ps.