Dynamics of nanoscopic hydrogen bonding systems probed using ultrafast nonlinear infrared spectroscopy

Hydrogen bonded liquids are interesting not only because of their ubiquity in chemistry and biology but also because the intermolecular interactions give rise to numerous anomalous phenomena. Infrared (IR) spectroscopy is ideally suited to study the structure and dynamics of hydrogen bonded liquids because vibrational modes are sensitive to the presence of hydrogen bonding.; One of the simplest hydrogen bonded systems in a liquid consists of alcohols dissolved in carbon tetrachloride. The dynamics of nanoscopic chains of hydrogen bonded methanol molecules were studied using pump-probe spectroscopy. Vibrational lifetimes, orientational relaxation and spectral diffusion of hydrogen bonded methanol molecules were all measured and determined to be affected by the presence of hydrogen bonds.; Another fundamentally interesting hydrogen bonded system consists of confining water molecules to spherical Aerosol-OT (AOT) reverse micelles whose sizes are readily tunable. All the time resolved data indicate that energy and structural relaxation slow down dramatically with reverse micelle size. Bulk water characteristics are approached at reverse micelle sizes of 7 nanometers in diameter. A core/shell model of water confined within was implemented to attempt to explicate the data. The shell is assumed to contain immobilized water molecules well represented by water molecules confined to the smallest reverse micelle studied. The core consists of bulk-like water with similar bulk-like dynamical features. The IR spectra and vibrational lifetimes are well described by the core/shell model while the orientational anisotropies and spectral diffusion cannot be modeled using this two-ensemble picture. It is proposed that when hydrogen bond structural rearrangement is involved (orientational relaxation and spectral diffusion) dynamical coupling between the shell and the core cause the water nanopool to display more spatially homogeneous dynamics.; Several other aqueous chemical environments were studied to determine what factors influence the dynamics of water. The systems were formulated to have essentially the same IR absorption spectra. The energy and structural rearrangements vary significantly between the samples illustrating the utility of nonlinear spectroscopies in probing the dynamics of water.