Ultrafast structural fluctuations and rearrangements of water's hydrogen bonded network

Aqueous chemistry is strongly influenced by water's ability to form an extended network of hydrogen bonds. It is the fluctuations and rearrangements of this network that stabilize reaction products and drive the transport of excess protons through solution. Experimental observations of the dynamics of the hydrogen bonded network are difficult because (1) the timescales are exceedingly fast with relevant fluctuations occurring on a tens of femtosecond period and (2) the experimental probe must be sensitive to the local hydrogen bonded structure. In this thesis I address these experimental challenges through the development of ultrafast nonlinear infrared spectroscopy of the OH stretch of HOD in D20. The frequency of the OH stretch, OH, is sensitive to the configuration of the hydrogen bonded pair. Therefore, time-dependent changes in OoH can be correlated with changes in the hydrogen bonded geometry. I describe how broadband homodyne echo and polarization-dependent pump-probe experiments can be utilized to separate the contributions of spectral diffusion, vibrational relaxation and molecular reorientation. These experiments observe the underdamped motion of the hydrogen bonded pair and the librational motion of the OH dipole on the 180 and 50 fs timescales, respectively.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Chemistry.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2007

Author dc:creator

• Loparo, Joseph J. (Joseph John)

Advisor dc:contributor.advisor

• Andrei Tokmakoff.

• Chemistry.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/38623

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/38623