No doubt, water is the most important liquid on the planet. In addition to the obligatory need for water in life, water is widely used in diverse applications. In most applications if not all, water is interfaced with different materials, at different phases depending on the application. This unique value of water originates from its chemical structure, which is based on hydrogen bonding. Although these chemical bonding in bulk liquid and vapor water have extensively been investigated, in interfacial water are not yet fully understood. This thesis presents an investigation of ultrafast vibrational dynamics of hydrogen bonding in interfacial water. In a first chapter, the experimental technique and tools needed for the study of interfacial vibrational dynamics are exposed. In the first part of a second chapter, vibrational coherence dynamics of free OH stretch modes at the alumina/water interface are investigated. And in the second part, vibrational coherence dynamics of hydrogen bonded OH stretch modes at the calcium fluoride/water interface are investigated. To understand the dynamics of vibrational energy flow within an interfacial network of hydrogen bonding, the investigation of vibrational coupling dynamics at the calcium fluoride/water interface takes place in a third chapter. Unlike what has already been reported in this topic, in our work, the vibrational energy will be initially deposited at the second vibrational excited state, through an overtone transition.

Chemistry

This thesis presents a highly innovative study of the ultrafast structural and vibrational dynamics of hydrated phospholipids, the basic constituents of cell membranes. As a novel approach to the water-phospholipid interface, the author studies phosphate vibrations using the most advanced methods of nonlinear vibrational spectroscopy, including femtosecond two-dimensional infrared spectroscopy. He shows for the first time that the structure of interfacial water undergoes very limited fluctuations on a 300 fs time scale and that the lifetimes of hydrogen bonds with the phospholipid are typically longer than 10 ps. Such properties originate from the steric hindrance of water fluctuations at the interface and the orienting action of strong electric fields from the phospholipid head group dipoles. In an extensive series of additional experiments, the vibrational lifetimes of the different vibrations and the processes of energy dissipation are elucidated in detail.

"We survey the dynamics of the interfacial water at the air/water interface. We reveal that the ultrafast vibrational energy transfer dynamics and spectral diffusion of the OH stretch mode at the interface differs from those in the bulk significantly; the rotational motion is 3 times faster than in the bulk and energy relaxation is dominated by the rotational dynamics as well as the vibrational energy transfer from the free OH group to the H-bonded OH groups of a water molecule with the free OH group. These insights can only be obtained by conducting the time-resolved surface-specific spectroscopic studies presented in this thesis."--Samenvatting auteur.

Multidimensional IR spectroscopy has the power to demystify molecular dynamics in the liquid phase. It allows a glimpse beneath the broadened spectral lineshapes of molecular liquids giving insight into the internal mechanisms of energy transfer and decoherence. An excellent candidate of this technique is liquid H2O, whose importance to chemistry and biology cannot be understated. Little is known about the time resolved dynamics of this liquid and the hydrogen bonding network which is responsible for its anomalous properties. This lack of previous experimental work is due to the inherent difficulty of performing ultrafast studies on the vibrational transitions of H2O in the condensed phase. In this work, two-dimensional infrared photon echo measurements of the OH stretching vibration in liquid water are performed at various temperatures. The temperature dependence of energy dynamics is of particular interest because it can isolate the effect of the hydrogen bonding network on the intermolecular dynamics. New insight into the hydrogen bonding network are revealed by the spectroscopic behaviour of this hydrogen bonded liquid. It is found that within the pure 'liquid spectral diffusion and resonant energy transfer occur on a time scale much shorter than the average hydrogen bond lifetime. Room temperature measurements show a loss of frequency and, thus, structural correlations on a 50 fs timescale. Weakly hydrogen bonded OH stretching oscillators absorbing at high frequencies undergo slower spectral diffusion than strongly bonded oscillators. With decreasing temperature the loss in memory slows down. Near freezing the frequency correlations in the OH stretch vibration persist beyond & sim; 200 fs, pointing to a reduction in dephasing by librational excitations. Polarization resolved purnp-probe studies give a resonant intermolecular energy transfer time of 80 fs which is unaffected by temperature. At low temperature, structural correlations persist longer than the energy transfer time, suggesting new evidence for a delocalization of OH stretching excitations over many water molecules and exciton-like behaviour for the primary excitation of water, a distinctly quantum mechanical effect.

The advent of laser-based sources of ultrafast infrared pulses has extended the study of very fast molecular dynamics to the observation of processes manifested through their effects on the vibrations of molecules. In addition, non-linear infrared spectroscopic techniques make it possible to examine intra- and intermolecular interactions and how such interactions evolve on very fast time scales, but also in some instances on very slow time scales. Ultrafast Infrared Vibrational Spectroscopy is an advanced overview of the field of ultrafast infrared vibrational spectroscopy based on the scientific research of the leading figures in the field. The book discusses experimental and theoretical topics reflecting the latest accomplishments and understanding of ultrafast infrared vibrational spectroscopy. Each chapter provides background, details of methods, and explication of a topic of current research interest. Experimental and theoretical studies cover topics as diverse as the dynamics of water and the dynamics and structure of biological molecules. Methods covered include vibrational echo chemical exchange spectroscopy, IR-Raman spectroscopy, time resolved sum frequency generation, and 2D IR spectroscopy. Edited by a recognized leader in the field and with contributions from top researchers, including experimentalists and theoreticians, this book presents the latest research methods and results. It will serve as an excellent resource for those new to the field, experts in the field, and individuals who want to gain an understanding of particular methods and research topics.

Water dynamics near interfaces and in confined systems, as manifested by vibrational relaxation, orientational relaxation, and spectral diffusion of the water hydroxyl stretch (5% HOD in H2O), are measured via infrared (IR) pump-probe and 2D IR vibrational echo techniques. It is shown that a two component model for population and orientational relaxation accurately describes the dynamics for systems comprised of two types of hydrogen bonding ensembles: waters that are hydrogen bonded to other waters and waters at an interfacial region. Through a combination of spectroscopic and data analysis techniques, the dynamics of these two environments become separable. This two component model is successfully applied to binary mixtures of water and tetraethylene glycol dimethyl ether. The effects of confinement on water dynamics are studied by examining water inside of reverse micelles made with the surfactant Aerosol-OT (AOT), which contains charged head groups. Large reverse micelles (diameter [greater than or equal to] 4.6 nm) can be decomposed into two separate environments: a bulk water core and an interfacial water shell. Each region has distinct dynamics that can be resolved experimentally using the two component model. The core follows bulk water dynamics while interfacial water shows slower dynamics that are independent of size for large reverse micelles. To explore how the chemical composition of the interface influences dynamics, the dynamics of water in AOT reverse micelles are compared to water dynamics in reverse micelles made from the neutral surfactant Igepal CO-520. It is found that the presence of an interface plays the major role in determining interfacial water dynamics and not the chemical composition. A two component model is also developed for spectral diffusion. The two component model for spectral diffusion is an extended version of the center line slope (CLS) analysis procedure, originally developed for single ensemble systems. The modified two component CLS procedure allows the CLS behavior of water at the interface to be back-calculated from known parameters. From the interfacial CLS, the interfacial frequency-frequency correlation function, which describes spectral diffusion, can be determined. It is found that, similar to orientational relaxation behavior in large AOT reverse micelles, the interfacial FFCF does not vary with increasing reverse micelle size.