Matrix Isolation Infrared Spectroscopy and Ab Initio SCF Calculations of Hydrogen Bonded Complexes PDF Download
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Author: Steven Roberts Davis
Publisher:
ISBN:
Category : Cryochemistry
Languages : en
Pages : 388
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Author: Steven Roberts Davis
Publisher:
ISBN:
Category : Cryochemistry
Languages : en
Pages : 388
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Author: Anders S. Engdahl
Publisher:
ISBN:
Category : Chemical bonds
Languages : en
Pages : 42
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Book Description
Abstract: A number of matrix isolated binary hydrogen bonded complexes with water as on of the components have been investigated with FTIR spectroscopy in the mid and far infrared regions. Water has been found to be the hydrogen bond donor in complexes with water, ammonia, dimethyl ether, and acetone. With formanide two equally strong hydrogen bonds are formed one from water to the to the carbonyl oxygen and one from an amide hydrogen to the water oxygen. In the formic acid water complex the strongest bond is from formic acid to water but there is also a second bond where the water acts as the proton donor. HDO prefers as usual to be D-bonded in the studied complexes. A model developed in cooperation with the Theoretical Chemistry Department has been used to make ab initio calculations on the observed complexes. The six intermolecular fundamentals of the complexes have been characterized with this model. It has been found that it is possible to make a quite simple description that holds for all complexes where water is one of the complex partners. Even for the formamide water complex with its cyclic structure the description is valid, but for the formic acid water complex the description fails. In this complex all the intermolecular vibrations, except for the hydrogen bond stretch that is quite pure, are heavily mixed. A new method for infrared laser irradiation has been tested on water dimers and on the formaldehyde water complex. With this tool it was possible to see an intermolecular fundamental of the water dimer.
Author: Petr Carsky
Publisher: Springer Science & Business Media
ISBN: 3642931405
Category : Science
Languages : en
Pages : 256
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Book Description
Until recently quantum chemical ab initio calculations were re stricted to atoms and very small molecules. As late as in 1960 Allen l and Karo stated : "Almost all of our ab initio experience derives from diatomic LCAO calculations ••• N and we have found in the litera ture "approximately eighty calculations, three-fourths of which are for diatomic molecules ••• There are approximately twenty ab initio calculations for molecules with more than two atoms, but there is a decided dividing line between the existing diatomic and polyatomic wave functions. Confidence in the satisfactory evaluation of the many -center two-electron integrals is very much less than for the diatom ic case". Among the noted twenty calculations, SiH was the largest 4 molecule treated. In most cases a minimal basis set was used and the many-center two-electron integrals were calculated in an approximate way. Under these circumstances the ab initio calculations could hard ly provide useful chemical information. It is therefore no wonder that the dominating role in the field of chemical applications was played by semiempirical and empirical methods. The situation changed essentially in the next decade. The problem of many-center integrals was solved, efficient and sophisticated computer programs were devel oped, basis sets suitable for a given type of problem were suggested, and, meanwhile, a considerable amount of results has been accumulated which serve as a valuable comparative material. The progress was of course inseparable from the development and availability of computers.
Author: Steve Scheiner
Publisher: Oxford University Press, USA
ISBN: 019509011X
Category : Science
Languages : en
Pages : 396
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Book Description
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.
Author: Rui Fausto
Publisher: Springer Science & Business Media
ISBN: 9400902816
Category : Science
Languages : en
Pages : 622
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Book Description
Molecular spectroscopy has achieved rapid and significant progress in recent years, the low temperature techniques in particular having proved very useful for the study of reactive species, phase transitions, molecular clusters and crystals, superconductors and semiconductors, biochemical systems, astrophysical problems, etc. The widening range of applications has been accompanied by significant improvements in experimental methods, and low temperature molecular spectroscopy has been revealed as the best technique, in many cases, to establish the connection between experiment and theoretical calculations. This, in turn, has led to a rapidly increasing ability to predict molecular spectroscopic properties. The combination of an advanced tutorial standpoint with an emphasis on recent advances and new perspectives in both experimental and theoretical molecular spectroscopy contained in this book offers the reader insight into a wide range of techniques, particular emphasis being given to supersonic jet and matrix isolation techniques, spectroscopy in cryogenic solutions (including liquid noble gases), and in both crystalline and amorphous states. Suitable quantum chemical methods are also considered, as are empirically based force field methods for calculating spectra of large molecular systems. The wide range of topics covered includes: molecular dynamics and reactivity, time-resolved and high-resolution spectroscopy, conformational analysis, hydrogen bonding and solvent effects, structure and dynamics of weakly bound complexes, transition metal and organic photochemistry, spectroscopy of excited states, ab initio prediction of molecular spectra, and biochemical and astrophysical applications.
Author: Bruce Stafford Ault
Publisher:
ISBN:
Category :
Languages : en
Pages : 398
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Author: Rodney Dale Hunt
Publisher:
ISBN:
Category : Fourier transform infrared spectroscopy
Languages : en
Pages : 282
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Author: Claire Louise Spencer
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
A blue shift in the CH stretching vibration of formic acid cyclic dimer of 6.6 ern" (symmetric) and 3 ern" (antisymmetric) is observed by high resolution Raman (symmetric) and infrared (antisymmetric) spectroscopy. This is corroborated by theoretical ab initio calculations where blue shifts in the CH stretching vibration of 12.79 ern" (symmetric) and 10.26 ern" (antisymmetric) are calculated (CP corrected MP2/6-311++G(d,p) level of theory). This is unusual due to the CH bond not playing a direct part in the bonding of the dimer. The electric dipole moment derivative curve with respect to bond length of the CH bond in formic acid is found to be unusual. The equilibrium bond length is on the negative gradient side of the maximum of the dipole, and this has been used to explain interesting behaviour observed, including the blue shift of the CH stretching vibration and how the contribution of electrostatics to the interaction energy can cause a blue shift of the stretching vibration in the spectrum. A mechanism is proposed where the electron density is transferred from the CH bond, through to the OH site where bonding does take place. This in turn causes the CH bond to have increased polarity, and therefore the bond contracts due to this interaction. Several chloroform complexes are investigated, which show either blue shifting or red shifting of the CH stretching vibration. Complexation with dimethyl ether shows an experimental red shift of the CH stretching vibration of chloroform of -1.5 ern", and a theoretical shift of -2.11 crn'. The complex of chloroform with trimethyl amine shows an experimental red shift of the CH stretching vibration of chloroform of -54 ern", and a theoretical prediction of -79.51 ern". Both of these complexes show a 1: 1 stoichiometric equation. The chloroform self dimer shows blue shifts in the CH stretching vibration, calculated to be 2.1 and 8.8 ern", experimental results are currently inconclusive. Morokuma Kitaura energy decomposition has been used to understand the energy contributions to intermolecular bonding. Electrostatic interaction and exchange repulsion have been shown to be the main contributions to bonding, but some unusual cases, for example the CH bond of formic acid cyclic dimer, have shown electrostatics to cause a blue shift. - 3 - A tuneable stimulated Raman photoacoustic spectroscopy (PARS) set up has been further applied to the trace detection of H2' and has achieved a detection limit of 6.69 ppm by volume. A non-dispersive Raman shifter method has also been investigated as a simpler alternative to the tuneable PARS set up and has achieved a less sensitive detection limit of 108 ppm by volume. Methane has also been detected qualitatively via this method, using the Raman shifter as a source of infrared light.
Author:
Publisher:
ISBN:
Category : Dissertations, Academic
Languages : en
Pages : 884
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Author: C. C. Addison
Publisher: Royal Society of Chemistry
ISBN: 0851867626
Category : Chemical elements
Languages : en
Pages : 741
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Book Description
Specialist Periodical Reports provide systematic and detailed review coverage of progress in the major areas of chemical research. Written by experts in their specialist fields the series creates a unique service for the active research chemist, supplying regular critical in-depth accounts of progress in particular areas of chemistry. For over 80 years the Royal Society of Chemistry and its predecessor, the Chemical Society, have been publishing reports charting developments in chemistry, which originally took the form of Annual Reports. However, by 1967 the whole spectrum of chemistry could no longer be contained within one volume and the series Specialist Periodical Reports was born. The Annual Reports themselves still existed but were divided into two, and subsequently three, volumes covering Inorganic, Organic and Physical Chemistry. For more general coverage of the highlights in chemistry they remain a 'must'. Since that time the SPR series has altered according to the fluctuating degree of activity in various fields of chemistry. Some titles have remained unchanged, while others have altered their emphasis along with their titles; some have been combined under a new name whereas others have had to be discontinued. The current list of Specialist Periodical Reports can be seen on the inside flap of this volume.
