Ultrafast IR-Raman spectroscopy with a mid-IR pump and an incoherent anti-Stokes Raman probe has been used to investigate the vibrational relaxation of water in various hydrogen-bonding environments. The vibrational relaxation (VR) dynamics of water and HOD/D2O has been studied in depth to understand a relationship between the excited state vibrational spectrum of water and hydrogen-bonding environments. A long-lived (T 1 > 200 ps) interfacial vibration of water has been found in the ablation process by a mid-IR pulse at nuOH absorption maximum. Vibrational spectra of excited states nuOH and metastable H2O* have also been measured. Metastable H2O* shows a spectrum like supercritical water at ∼600 K and relaxes with 0.8 ps lifetime by the reformation of the disrupted hydrogen-bond network.

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.

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.

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.

A unified overview of the dynamical properties of water and its unique and diverse role in biological and chemical processes.

This unique volume presents a comprehensive but accessible introduction to the field of ultrafast two-dimension infrared (2D IR) vibrational echo spectroscopy based on the pioneering work of Professor Michael D Fayer, Department of Chemistry, Stanford University, USA. It contains in one place a qualitative introduction to the field of 2D IR spectroscopy and a comprehensive set of scientific papers that underlie the qualitative discussion. The introductory material contains several detailed illustrations, and is based on the Centenary Lecture at the Indian Institute of Science given by Professor Fayer July 16, 2008 as part of the celebration of the 100th anniversary of the founding of IIS in Bangalore, India. The second part of the volume contains reprints of Fayer's relevant papers. The compilation will be very useful because it presents the historical background, motivation, methodology, and experimental results at a level that is accessible to the non-expert. The reprints of the scientific papers, from review articles to detailed theoretical papers, provide rigorous supporting material so that the reader can delve as deeply as desired into the subject.