Vibrational Dynamics in Water from the Molecule's Perspective

Vibrational Dynamics in Water from the Molecule's Perspective
Author: Joel David Eaves
Publisher:
Total Pages: 227
Release: 2005
Genre:
ISBN:

Download Vibrational Dynamics in Water from the Molecule's Perspective Book in PDF, Epub and Kindle

(Cont.) Because electric fields drive vibrational dephasing, the frequency of the OH stretch is particularly sensitive to the microscopic details of the molecular potential. With collaborators, I have examined the accuracy of emerging fluctuating charge models for water and the role that molecular polarizability plays in the vibrational spectroscopy. In liquid water at ambient conditions, roughly 90 % of the hydrogen bonds are intact. I have examined the fates and the fundamental chemical nature of the remaining 10 % of the "broken" hydrogen bonds. We consider two reaction mechanisms that describe how hydrogen bonds change partners. In the first scenario, broken hydrogen bonds exist in stable chemical equilibrium with intact hydrogen bonds. In an alternate scenario, the broken hydrogen bond is not a meta-stable chemical state but instead a species that molecules visit during natural equilibrium fluctuations or when trading hydrogen bonding partners. I show how the methods of condensed phase reaction dynamics can be directly applied to vibrational spectroscopy of reactive systems and how experimental 2D IR spectra can distinguish between the two mechanistic scenarios. Our data support the notion that broken hydrogen bonds are an intrinsically unstable species in water and return to form hydrogen bonds on the time scale of intermolecular motions.

Vibrational Dynamics Of Molecules

Vibrational Dynamics Of Molecules
Author: Joel M Bowman
Publisher: World Scientific
Total Pages: 603
Release: 2022-06-14
Genre: Science
ISBN: 9811237921

Download Vibrational Dynamics Of Molecules Book in PDF, Epub and Kindle

Vibrational Dynamics of Molecules represents the definitive concise text on the cutting-edge field of vibrational molecular chemistry. The chapter contributors are a Who's Who of world leaders in the field. The editor, Joel Bowman, is widely considered as one of the founding fathers of theoretical reaction dynamics. The included topics span the field, from fundamental theory such as collocation methods and vibrational CI methods, to interesting applications such as astrochemistry, supramolecular systems and virtual computational spectroscopy. This is a useful reference for theoretical chemists, spectroscopists, physicists, undergraduate and graduate students, lecturers and software developers.

Water in Biological and Chemical Processes

Water in Biological and Chemical Processes
Author: Biman Bagchi
Publisher: Cambridge University Press
Total Pages: 383
Release: 2013-11-14
Genre: Medical
ISBN: 1107037298

Download Water in Biological and Chemical Processes Book in PDF, Epub and Kindle

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

Structures and Dynamics of Interfacial Water

Structures and Dynamics of Interfacial Water
Author: Fujie Tang
Publisher:
Total Pages:
Release: 2019
Genre: Biological interfaces
ISBN: 9789811389665

Download Structures and Dynamics of Interfacial Water Book in PDF, Epub and Kindle

This book focuses on the study of the interfacial water using molecular dynamics simulation and experimental sum frequency generation spectroscopy. It proposes a new definition of the free O-H groups at water-air interface and presents research on the structure and dynamics of these groups. Furthermore, it discusses the exponential decay nature of the orientation distribution of the free O-H groups of interfacial water and ascribes the origin of the down pointing free O-H groups to the presence of capillary waves on the surface. It also describes how, based on this new definition, a maximum surface H-bond density of around 200 K at ice surface was found, as the maximum results from two competing effects. Lastly, the book discusses the absorption of water molecules at the water-TiO2 interface. Providing insights into the combination of molecular dynamics simulation and experimental sum frequency generation spectroscopy, it is a valuable resource for researchers in the field.

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 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 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.

Ab Initio Molecular Dynamics

Ab Initio Molecular Dynamics
Author: Dominik Marx
Publisher: Cambridge University Press
Total Pages: 503
Release: 2009-04-30
Genre: Science
ISBN: 1139477196

Download Ab Initio Molecular Dynamics Book in PDF, Epub and Kindle

Ab initio molecular dynamics revolutionized the field of realistic computer simulation of complex molecular systems and processes, including chemical reactions, by unifying molecular dynamics and electronic structure theory. This book provides the first coherent presentation of this rapidly growing field, covering a vast range of methods and their applications, from basic theory to advanced methods. This fascinating text for graduate students and researchers contains systematic derivations of various ab initio molecular dynamics techniques to enable readers to understand and assess the merits and drawbacks of commonly used methods. It also discusses the special features of the widely used Car–Parrinello approach, correcting various misconceptions currently found in research literature. The book contains pseudo-code and program layout for typical plane wave electronic structure codes, allowing newcomers to the field to understand commonly used program packages and enabling developers to improve and add new features in their code.

Structures and Dynamics of Interfacial Water

Structures and Dynamics of Interfacial Water
Author: Fujie Tang
Publisher: Springer
Total Pages: 93
Release: 2019-06-20
Genre: Science
ISBN: 9811389659

Download Structures and Dynamics of Interfacial Water Book in PDF, Epub and Kindle

This book focuses on the study of the interfacial water using molecular dynamics simulation and experimental sum frequency generation spectroscopy. It proposes a new definition of the free O-H groups at water-air interface and presents research on the structure and dynamics of these groups. Furthermore, it discusses the exponential decay nature of the orientation distribution of the free O-H groups of interfacial water and ascribes the origin of the down pointing free O-H groups to the presence of capillary waves on the surface. It also describes how, based on this new definition, a maximum surface H-bond density of around 200 K at ice surface was found, as the maximum results from two competing effects. Lastly, the book discusses the absorption of water molecules at the water–TiO2 interface. Providing insights into the combination of molecular dynamics simulation and experimental sum frequency generation spectroscopy, it is a valuable resource for researchers in the field.