Ultrafast Vibrational Dynamics of Liquid Water

Ultrafast Vibrational Dynamics of Liquid Water
Author: Darren Kraemer
Publisher:
Total Pages: 322
Release: 2008
Genre:
ISBN: 9780494397855

Download Ultrafast Vibrational Dynamics of Liquid Water Book in PDF, Epub and Kindle

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.

Ultrafast Vibrational Dynamics at the Solid/Water Interface

Ultrafast Vibrational Dynamics at the Solid/Water Interface
Author: Abdelaziz Boulesbaa
Publisher:
Total Pages: 87
Release: 2014
Genre:
ISBN:

Download Ultrafast Vibrational Dynamics at the Solid/Water Interface Book in PDF, Epub and Kindle

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.

Ultrafast Infrared Vibrational Spectroscopy

Ultrafast Infrared Vibrational Spectroscopy
Author: Michael D. Fayer
Publisher: CRC Press
Total Pages: 491
Release: 2013-03-04
Genre: Science
ISBN: 1466510137

Download Ultrafast Infrared Vibrational Spectroscopy Book in PDF, Epub and Kindle

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.

Ultrafast Dynamics of Water in Nonaqueous Liquids

Ultrafast Dynamics of Water in Nonaqueous Liquids
Author: Daryl Brian Wong
Publisher:
Total Pages:
Release: 2013
Genre:
ISBN:

Download Ultrafast Dynamics of Water in Nonaqueous Liquids Book in PDF, Epub and Kindle

The dynamic structure of water and its hydrogen bond network are important in nature. Water molecules make highly directed hydrogen bonds that allow it to form extended hydrogen bond networks in the bulk. In this extended network, water's directional hydrogen bonds are readily fluctuating and exchanging. When interacting with molecules other than itself, water behaves differently than what is observed in the bulk. The dynamics of water molecules in a heterogeneous environment is dictated in large part by the size and hydrogen bonding nature of the interacting non-water species. While water still forms directed hydrogen bonds in heterogeneous environments, the dynamics of the water molecules are altered by disruption of water's extended hydrogen bond network. The studies described herein are concerned with how water's orientational and structural dynamics change as it interacts with non-water species in solution which has relevance to chemical and biological systems. Ultrafast infrared spectroscopic techniques are used to examine water and its hydrogen bonding network. These methods interrogate molecular systems with femtosecond infrared pulses which can probe the dynamics of water molecules (100s of fs to ps) on the time scale with which they move. Changes in local molecular structure can be monitored by observing changes in vibrational frequency. The stretching mode of deuterated hydroxyl (OD) groups serves as the vibrational probe for the experiments. In these studies, both two-dimensional infrared vibrational echo (2D IR) spectroscopy and polarization selective pump-probe spectroscopy are employed to monitor the dynamics of water molecules in non-aqueous environments. The pump-probe experiments provide information on both the vibrational lifetime and orientational relaxation of water molecules within the sample. 2D IR experiments characterize the spectral diffusion of the vibrational mode through the frequency-frequency correlation function (FFCF) which monitors the structural evolution of water's hydrogen bonds. The dynamics of water in two systems are discussed in this thesis. The first study examines the dynamics of dimethyl sulfoxide (DMSO)/water solutions over a wide range of water concentrations. Both linear IR absorption spectra and vibrational population relaxation studies show that water-water and water-DMSO interactions are present, even at very low water concentration. Though water forms multiple hydrogen bonding partners, observation of a single ensemble anisotropy indicates the concerted reorientation between water and DMSO molecules in solution. In addition to OHD-OKE experiments, which track the orientational relaxation timescales to be similar to that of water suggests that the reorientation of water is coupled to that of the DMSO molecules in solution. Interpretation of FFCF measurements from the 2D IR experiment shows fast, local hydrogen bond fluctuations and slower longer structural fluctuations associated with global hydrogen bond rearrangement. In the second system, the vibrational dynamics of spatially isolated water molecules were examined in the room temperature ionic liquid (RTIL) 1-butyl-3-methylimidazolium hexafluorophosphate (BmImPF6). The antisymmetric and symmetric modes of D2O are well resolved, which is unusual for the condensed phase. The spectral separation of the two peaks make it possible to study the inter and intramolecular dynamics of a vibrationally excited water molecule. Examination of the intramolecular dynamics focused mainly on the redistribution of vibrational energy throughout the water molecule. Both population exchange between vibrational modes and excited-state relaxation were monitored to determine the timescales vibrational energy exchange and relaxation. In addition, coherent quantum beats were observed in short time amplitude and frequency correlation trajectories. Oscillations in the crosspeak shape, from highly correlated to slightly anti-correlated, show that coherent transfer of energy between the two modes occurs in a slightly anti-correlated fashion. The slight anti-correlation can be explained by a distribution in the coupling strength between the local hydroxyl modes. The water's dynamics as influenced by the surrounding salt molecules was examined using both FFCF of the crosspeak shape as well as the orientational relaxation. Timescales for orientational relaxation and structural rearrangements of the isolated water molecules within solution were determined.

Ultrafast Dynamics of Phospholipid-Water Interfaces

Ultrafast Dynamics of Phospholipid-Water Interfaces
Author: René Costard
Publisher: Springer
Total Pages: 112
Release: 2015-08-08
Genre: Science
ISBN: 3319220667

Download Ultrafast Dynamics of Phospholipid-Water Interfaces Book in PDF, Epub and Kindle

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.

Ultrafast Vibrational Dynamics of Water and Confined Water in Reverse Micelles

Ultrafast Vibrational Dynamics of Water and Confined Water in Reverse Micelles
Author: Yoonsoo Pang
Publisher: ProQuest
Total Pages: 183
Release: 2007
Genre:
ISBN: 9780549344162

Download Ultrafast Vibrational Dynamics of Water and Confined Water in Reverse Micelles Book in PDF, Epub and Kindle

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.