Download or read book Infrared Vibrational Predissociation Spectroscopy of Water Clusters by the Crossed Laser Molecular Beam Technique written by and published by . This book was released on 1981 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water clusters formed in a molecular beam are predissociated by tunable, pulsed, infrared radiation in the frequency range 2900~3750 cm−1. The recoiling fragments are detected off axis from the molecular beam using a rotatable mass spectrometer. Arguments are presented which show that the measured frequency dependent signal at a fixed detector angle is proportional to the absorption spectrum of the clusters. It is found that the spectra of clusters containing three or more water molecules are remarkably similar to the liquid phase spectrum. Dynamical information on the predissociation process is obtained from the velocity distribution of the fragments. An upper limit to the excited vibrational state lifetime of ~1 microsecond is observed for the results reported here. The most probable dissociation process concentrates the available excess energy into the internal motions of the fragment molecules. Both the time scale and translational energy distribution are consistent with the qualitative predictions of current theoretical models for cluster predissociation. From adiabatic dissociation trajectories and Monte Carlo simulations it is seen that the strong coupling present in the water polymers probably invalidates the simpler "diatomic" picture formulations of cluster predissociation. Instead, the energy can be extensively shared among the intermolecular motions in the polymer before dissociation. Comparison between current intermolecular potentials describing liquid water and the observed frequencies is made in the normal mode approximation. The inability of any potential to predict the gross spectral features (the number of bands and their observed frequency shift from the gas phase monomer) suggests that substantial improvement in the potential energy functions are possible, but that more accurate methods of solving the vibrational wave equation are necessary before a proper explanation of the spectral fine structure is possible. The observed differences between the dimer and larger polymers (trimer-hexamer) indicate a dramatic change in the hydrogen bonding, which is best explained as arising from the non-additive effects present when a water molecule is both donating and accepting a hydrogen bond. This difference between dimer and trimer also rationalizes the previous disagreement between potential functions based on condensed phase properties (where the water molecule is interacting with multiple neighbors) and those fit to imperfect gas or dimer properties which sample only the isolated pair potential. The data support an interpretation of the hydrogen bonded O-H stretching fundamental region as arising from a homogeneous broadening (not necessarily a result of the predissociation) whose width is characteristic of the hydrogen bond itself and not the sum of distinct bonding geometries. This is different from some previous theories of the water infrared absorption spectrum which assign each band to water molecules bound to different numbers of neighboring molecules.
Download or read book Vibrational Predissociation of Benzene Dimers and Trimers by the Crossed Laser molecular Beam Technique written by and published by . This book was released on 1981 with total page 7 pages. Available in PDF, EPUB and Kindle. Book excerpt: Water clusters formed in a molecular beam are predissociated by tunable, pulsed, infrared radiation in the frequency range 29003̃750 cm−1. The recoiling fragments are detected off axis from the molecular beam using a rotatable mass spectrometer. Arguments are presented which show that the measured frequency dependent signal at a fixed detector angle is proportional to the absorption spectrum of the clusters. It is found that the spectra of clusters containing three or more water molecules are remarkably similar to the liquid phase spectrum. Dynamical information on the predissociation process is obtained from the velocity distribution of the fragments. An upper limit to the excited vibrational state lifetime of 1̃ microsecond is observed for the results reported here. The most probable dissociation process concentrates the available excess energy into the internal motions of the fragment molecules. Both the time scale and translational energy distribution are consistent with the qualitative predictions of current theoretical models for cluster predissociation. From adiabatic dissociation trajectories and Monte Carlo simulations it is seen that the strong coupling present in the water polymers probably invalidates the simpler "diatomic" picture formulations of cluster predissociation. Instead, the energy can be extensively shared among the intermolecular motions in the polymer before dissociation. Comparison between current intermolecular potentials describing liquid water and the observed frequencies is made in the normal mode approximation. The inability of any potential to predict the gross spectral features (the number of bands and their observed frequency shift from the gas phase monomer) suggests that substantial improvement in the potential energy functions are possible, but that more accurate methods of solving the vibrational wave equation are necessary before a proper explanation of the spectral fine structure is possible. The observed differences between the dimer and larger polymers (trimer-hexamer) indicate a dramatic change in the hydrogen bonding, which is best explained as arising from the non-additive effects present when a water molecule is both donating and accepting a hydrogen bond. This difference between dimer and trimer also rationalizes the previous disagreement between potential functions based on condensed phase properties (where the water molecule is interacting with multiple neighbors) and those fit to imperfect gas or dimer properties which sample only the isolated pair potential. The data support an interpretation of the hydrogen bonded O-H stretching fundamental region as arising from a homogeneous broadening (not necessarily a result of the predissociation) whose width is characteristic of the hydrogen bond itself and not the sum of distinct bonding geometries. This is different from some previous theories of the water infrared absorption spectrum which assign each band to water molecules bound to different numbers of neighboring molecules.
Download or read book Raman Spectroscopy of Carboxylic Acid and Water Aggregates written by Zhifeng Xue and published by Logos Verlag Berlin GmbH. This book was released on 2011 with total page 262 pages. Available in PDF, EPUB and Kindle. Book excerpt: In the present work the carboxylic acid dimers and water clusters are chosen as model systems of strong and moderately strong hydrogen bonds and studied with spontaneous Raman spectroscopy coupled with a supersonic jet expansion. The spectra of several carboxylic acids are measured and assigned in the entire fundamental wavenumber region. An overview of their vibrations is achieved by comparing our experimental results with former experimental results as well as with quantum chemical calculations. For the first time, we know from experiment how anharmonic the hydrogen bond vibrations of formic acid are and it is proved that the hydrogen bond becomes stiffer when moving from formic acid to acetic acid. Now there is a very complete spectroscopic data base for formic acid dimer, which can be used to rigorously test quantum chemical calculations. Besides, we finally know from experiment how strongly the OH oscillators are coupled to each other in the simplest ring clusters of water. All this was only possible by the use of spontaneous Raman scattering in supersonic expansions, which is a really powerful tool to investigate hydrogen bonded systems.
Download or read book Energy Research Abstracts written by and published by . This book was released on 1993 with total page 638 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Practical Aspects of Computational Chemistry V written by Jerzy Leszczynski and published by Springer Nature. This book was released on 2021-10-21 with total page 292 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book presents contributions on a wide range of computational research applied to fields ranging from molecular systems to bulk structures. This volume highlights current trends in modern computational chemistry and discusses the development of theoretical methodologies, state-of-the-art computational algorithms and their practical applications. This volume is part of a continuous effort by the editors to document recent advances by prominent researchers in the area of computational chemistry. Most of the chapters are contributed by invited speakers and participants to International annual conference “Current Trends in Computational Chemistry”, organized by Jerzy Leszczynski, one of the editors of the current volume. This conference series has become an exciting platform for eminent theoretical and computational chemists to discuss their recent findings and is regularly honored by the presence of Nobel laureates. Topics covered in the book include reactive force-field methodologies, coarse-grained modeling, DNA damage radiosensitizers, modeling and simulation of surfaces and interfaces, non-covalent interactions, and many others. The book is intended for theoretical and computational chemists, physical chemists, material scientists and those who are eager to apply computational chemistry methods to problems of chemical and physical importance. It is a valuable resource for undergraduate, graduate and PhD students as well as for established researchers.
Download or read book Reviews in Computational Chemistry written by Kenny B. Lipkowitz and published by John Wiley & Sons. This book was released on 2009-09-22 with total page 464 pages. Available in PDF, EPUB and Kindle. Book excerpt: THIS BOOK HAS SIX TUTORIALS AND REVIEWS WRITTEN BY INVITED EXPERTS. FIVE CHAPTERS TEACH TOPICS IN QUANTUM MECHANICS AND MOLECULAR SIMULATIONS. THE SIXTH CHAPTER EXPLAINS HOW PROGRAMS FOR CHEMICAL STRUCTURE DRAWING WORK. AN EDITORIAL DISCUSSES SOME OF THE MOST WELL-KNOWN PERSONAGES IN COMPUTATIONAL CHEMISTRY. FROM REVIEWS OF THE SERIES "Anyone who is doing or intends to do computational research on molecular structure and design should seriously consider purchasing this book for his or her personal library."-JOURNAL OF COMPUTATIONAL CHEMISTRY. "These reviews are becoming regarded as the standard reference among both specialists and novices in the expanding field of computational chemistry." -JOURNAL OF MOLECULAR GRAPHICS AND MODELLING. "[This book is] written for newcomers learning about molecular modeling techniques as well as for seasoned professionals who need to acquire expertise in areas outside their own."-JOURNAL OF CHEMICAL INFORMATION AND COMPUTER SCIENCE.
Download or read book Hydrogen Bonding written by Steve Scheiner and published by Oxford University Press, USA. This book was released on 1997 with total page 396 pages. Available in PDF, EPUB and Kindle. Book excerpt: Because of the importance of the hydrogen bond, there have been scores of insights gained about its fundamental nature by quantum chemical computations over the years. Such methods can probe subtle characteristics of the electronic structure and examine regions of the potential energy surface that are simply not accessible by experimental means. The maturation of the techniques, codes, and computer hardware have permitted calculations of unprecedented reliability and rivaling the accuracy of experimental data. This book strives first toward an appreciation of the power of quantum chemistry to analyze the deepest roots of the hydrogen bond phenomenon. It offers a systematic and understandable account of decades of such calculations, focusing on the most important findings. This book provides readers with the tools to understand the original literature, and to perhaps carry out some calculations of their very own on systems of interest.
Download or read book Molecular Complexes In Earth s Planetary Cometary And Interstellar Atmospheres written by Zdenek Slanina and published by World Scientific. This book was released on 1998-07-04 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book introduces systematically the concept of weakly-bound complexes into the broad field of atmospheric sciences. To fill up the gap between our rapidly expanding knowledge of the individual properties of Van der Waals and hydrogen-bonded molecules, and our understanding of their role in the atmospheric processes, an ensemble of related topics are covered by a team of expert co-authors. The general properties of the weakly bound molecular complexes (or “clusters”) are discussed, as well as their distribution in the planetary atmospheres. Collision-induced and dimeric absorption and emission are considered in the context of atmospheric spectroscopy. The advanced experimental techniques which enable us to study the spectroscopic features of molecular complexes in the gas phase, or which are adsorbed, are reviewed. The role of molecular complexes in the cometary atmosphere, the Earth mesosphere, and the atmospheres of the giant planets and some of their satellites are also discussed in detail.
Download or read book Interactions of Water in Ionic and Nonionic Hydrates written by Hubertus Kleeberg and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 309 pages. Available in PDF, EPUB and Kindle. Book excerpt: There is no doubt about the importance of hydration in many areas of every day life, technology, biology, medicine, science etc. During the last years many investigations have been carried out upon problems of hydration and a large amount of experimental and theoretical data has been obtained by the application of different methods. One effi cient possibility to stimulate progress in scientific problems is to come together and discuss existing results and ideas. This was the aim of the 35th Bunsenkolloquium and a subsequent seminar held in Marburg, FRG from April 2 -4, 1987 with respect to the "Interaction of Water in Ionic and Nonionic Hydrates". The meeting was attended by more than one hundred participants from 25 countries. It will be seen from the content of the chapters in this book, which comprises the introductory papers and more or less extended abstracts of research seminars, that it was possible not only to stress the advantages and disadvantages of each method, but also to show how information gained by one method can complement the results of another one in order to increase our overall understanding of hydration pheno mena. The papers are divided into sections concerning the hydration of: ions, nonionic substances, biological and macromolecular substances, surfactants as well as a section containing methods, models and theo ries, which may stimulate investigations on hydrations.
Download or read book Physics Briefs written by and published by . This book was released on 1991 with total page 1454 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Far infrared Vibration rotation tunneling Spectroscopy of Cyclic Water Clusters written by Jeffrey Duane Cruzan and published by . This book was released on 1997 with total page 654 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book INIS Atomindex written by and published by . This book was released on 1996 with total page 730 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Scientific and Technical Aerospace Reports written by and published by . This book was released on 1989 with total page 1134 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Inventory of Federal Energy related Environment and Safety Research for written by and published by . This book was released on 1980 with total page 704 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Molecular Bean Scattering written by Matthew Fowler Vernon and published by . This book was released on 1983 with total page 790 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Book of Abstracts written by American Chemical Society. Meeting and published by . This book was released on 1986 with total page 1350 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Publications of the National Institute of Standards and Technology Catalog written by National Institute of Standards and Technology (U.S.) and published by . This book was released on 1994 with total page 1162 pages. Available in PDF, EPUB and Kindle. Book excerpt:
