Modern Optics and Spectroscopy
Andrei Tokmakoff, MIT
The fluctuations and switching of hydrogen bonds in water
April 10, 2007
12:00 noon - 1:00 p.m. Grier Room 34-401
Ultrafast infrared spectroscopy of the OH stretching vibration of HOD in D2O can be used to resolve the structural rearrangements of water’s hydrogen bonding network. Infrared spectroscopy of the OH stretch is an ideal technique because of its sensitivity to hydrogen bonding configurations. Conceptually our experiments aim to correlate the OH stretch frequency with the hydrogen bonded environment and then watch the time dependence of this frequency in order to report on the exchange of hydrogen bonding structures. Our studies reveal the vibrations and hindered rotational fluctuations of individual hydrogen bonds in water prior to a reconfiguration of the many-body liquid structure on picosecond time scales. Additionally, two-dimensional infrared spectroscopy of this transition provides information on the mechanism of hydrogen bond rearrangements. Our experimental results indicate that hydrogen bond switching is a concerted process in which a ruptured hydrogen bond appears only fleetingly as a transition state along the hydrogen bond switching coordinate.
TUESDAYS, 12:00-1:00, GRIER ROOM (34-401)
Refreshments served following the seminar
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Co-sponsored by the George R. Harrison
the Department of Electrical
Engineering and Computer Science and
the School of
Science, Massachusetts Institute