Unimolecular Reactions

Unimolecular Reactions Second Edition Kenneth A. Holbrook, University of Hull, UK Michael J. Pilling, University of Leeds, UK Struan H. Robertson, University of Leeds, UK Representing major advances in the area of gas kinetics in the last ...

Unimolecular Reactions

Representing major advances in this area of gas kinetics in the last twenty-five years, Unimolecular Reactions has been considerably rewritten to include important recent progress in both theory and experiment. New chapters cover the treatment of reactions with 'loose' transition states, the Master equation, and the approximate forms of Statistical Adiabatic Channel Theory. Extensive illustrations highlight both established activation methods and newer techniques such as the use of infrared and UV lasers, overtone excitation, molecular beam experiments and mass spectrometric methods.

Theory of Unimolecular Reactions

The last chapter is devoted to the transition state and its ambiguities. This text will be of interest to gas kineticists, mass spectrometrists, and students and researchers working in the field of physical chemistry.

Theory of Unimolecular Reactions

Theory of Unimolecular Reactions provides a comprehensive analysis of the theory of unimolecular reactions, also known to kineticists as the Rice-Marcus or the Rice-Ramsperger-Kassel-Marcus theory, and to those working in mass spectrometry and related fields as the quasi-equilibrium theory or the theory of mass spectra. This book demonstrates how theoretical parameters are related to experimental observables and describes the methods that are used to obtain useful numerical answers. This monograph consists of 11 chapters and begins by explaining the derivation of the expression for the basic rate k(E), with emphasis on the unimolecular rate constant, intramolecular energy transfer, and potential energy surfaces in unimolecular reactions. The statistical calculation of unimolecular rate under vibrational potential is also given, along with pertinent degrees of freedom. The remaining chapters explore the energy distribution functions appropriate to each system, the averaging of k(E), and the relations between theoretical and experimental parameters. Thermal reactions, chemical activation systems, and the theory of mass spectra are examined. The last chapter is devoted to the transition state and its ambiguities. This text will be of interest to gas kineticists, mass spectrometrists, and students and researchers working in the field of physical chemistry.

Unimolecular Reactions

Containing many problem sets and solutions, the book is targeted at graduate and advanced undergraduate students studying chemical dynamics, chemical kinetics and theoretical chemistry.

Unimolecular Reactions

The statistical theory of unimolecular reactions is now universally known as RRKM theory. This textbook covers the basics necessary for the understanding of RRKM theory in its original and variational, phase-space and angular momentum-conserved incarnations. After a review of the Kassel quantum model and the theory of Slater, the specific-energy RRKM rate constant k(E) is derived. The argument is then extended to the angular momentum-dependent rate constant k(E,J), to non-classical effects (tunneling and non-adiabatic transition), and the general problem of angular momentum conservation. A long chapter is devoted to the counting of quantum states. The chapter on thermal systems discusses both analytical and numerical solutions and is later extended to include the variational approach and discussion of exit channel effects. Containing many problem sets and solutions, the book is targeted at graduate and advanced undergraduate students studying chemical dynamics, chemical kinetics and theoretical chemistry.

Unimolecular Reaction Dynamics

This book provides a penetrating and comprehensive description of energy selected reactions from a theoretical as well as experimental view.

Unimolecular Reaction Dynamics

This book provides a penetrating and comprehensive description of energy selected reactions from a theoretical as well as experimental view. Three major aspects of unimolecular reactions involving the preparation of the reactants in selected energy states, the rate of dissociation of the activated molecule, and the partitioning of the excess energy among the final products, are fully discussed with the aid of 175 illustrations and over 1,000 references, most from the recent literature. Examples of both neutral and ionic reactions are presented. Many of the difficult topics are discussed at several levels of sophistication to allow access by novices as well as experts. Among the topics covered for the first time in monograph form is a discussion of highly excited vibrational/rotational states and intramolecular vibrational energy redistribution. Problems associated with the application of RRKM theory are discussed with the aid of experimental examples. Detailed comparisons are also made between different statistical models of unimolecular decomposition. Both quantum and classical models not based on statistical assumptions are described. Finally, a chapter devoted to the theory of product energy distribution includes the application of phase space theory to the dissociation of small and large clusters. The work will be welcomed as a valuable resource by practicing researchers and graduate students in physical chemistry, and those involved in the study of chemical reaction dynamics.

The Quantum Theory of Unimolecular Reactions

When this book was first published in 1984, the discovery of laser-induced mutliphoton chemical reactions had led to a resurgence of interest in the theory of unimolecular reactions.

The Quantum Theory of Unimolecular Reactions

When this book was first published in 1984, the discovery of laser-induced mutliphoton chemical reactions had led to a resurgence of interest in the theory of unimolecular reactions. Attempts to explain these phenomena had been built on a very imperfectly understood theory of thermal unimolecular reactions. In this book, Professor Pritchard presents a treatment that dissects the unimolecular reaction process into a sequence of distinct phases, so that the assumptions of the theory can be clearly seen, and confusion over the theory avoided. As such it provides a self-consistent foundation upon which to begin to treat these phenomena. Postgraduate students and research workers in physical chemistry will find this an invaluable textbook on a topic that has suddenly become of primary importance.

Unimolecular Kinetics

Such systems include combustion, industrial gas phase processes and atmospheric/environmental processes. The book also discusses The Master Equation to give a good overview of the mechanics underpinning unimolecular kinetics.

Unimolecular Kinetics

Unimolecular Kinetics: Part 2: Collisional Energy Transfer and the Master Equation, Volume 43 in Elsevier’s Comprehensive Molecular Kinetics series, addresses collision energy transfer and the effects it has on gas phase reactions, particularly at low gas density. Such systems include combustion, industrial gas phase processes and atmospheric/environmental processes. The book also discusses The Master Equation to give a good overview of the mechanics underpinning unimolecular kinetics. This new volume will be of interest to researchers investigating gas phase processes which involve unimolecular reactions and the related intermolecular reactions. Discusses collision energy transfer and the effects it has on gas phase reactions Introduces stochastic techniques to energy transfer methods, allowing for an extension of the unimolecular theory beyond simple molecular dissociation Draws an important connection between detailed reaction dynamic studies and the rate of coefficient determination

Competing Reaction Channels in IR laser induced Unimolecular Reactions

Ethylene loss is identified as the lowest energy reaction channel. Dehydrogenation is found to result from step-wise H atom loss. Isomerization via disproportionation is also identified as a primary reaction channel.

Competing Reaction Channels in IR laser induced Unimolecular Reactions

The competing reaction channels in the unimolecular decomposition of two molecules, formaldehyde and tetralin were studied. A TEA CO2 laser was used as the excitation source in all experiments. The dissociation of D2CO was studied by infrared multiphoton dissociation (MPD) and the small-molecule nature of formaldehyde with regard to MPD was explored. The effect of collisions in MPD were probed by the pressure dependence of the MPD yield and ir fluorescence from multiphoton excited D2CO. MPD yield shows a near cubic dependence in pure D2CO which is reduced to a 1.7 power dependence when 15 torr of NO is added. The peak amplitude of 5 .mu.m ir fluorescence from D2CO is proportional to the square of the D2CO pressure in pure D2CO or in the presence of 50 torr of Ar. Results are explained in terms of bottlenecks to excitation at the v = 1 level which are overcome by a combination of vibrational energy transfer and rotational relaxation. The radical/molecule branching ratio in D2CO MPD was 0.10 +- 0.02 at a fluence of 125 J/cm2 at 946.0 cm−1. The barrier height to molecular dissociation was calculated to be 3.6 +- 2.0 kcal/mole below the radical threshold or 85.0 +- 3.0 kcal/mole above the ground state of D2CO. In H2CO, this corresponds to 2.5 +- 2.0 kcal/mole below the radical threshold or 83.8 +- 3.0 kcal/mole above the ground state. Comparison with uv data indicate that RRKM theory is an acceptable description of formaldehyde dissociation in the 5 to 10 torr pressure range. The unimolecular decomposition of tetralin was studied by MPD and SiF4 - sensitized pyrolysis. Both techniques induce decomposition without the interference of catalytic surfaces. Ethylene loss is identified as the lowest energy reaction channel. Dehydrogenation is found to result from step-wise H atom loss. Isomerization via disproportionation is also identified as a primary reaction channel.

Comprehensive Chemical Kinetics

However, this is a rapidly developing field, and many new and important discoveries have been made in the past decade. This First Part Part of Two CCK Volumes dealing with Unimolecular Rections, deals with the Reaction Step.

Comprehensive Chemical Kinetics

Unimolecular reactions are in principle the simplest chemical reactions, because they only involve one molecule. The basic mechanism, in which the competition between the chemical reaction step and a collisional deactivation leads to a pressure-dependent coefficient, has been understood for a long time. However, this is a rapidly developing field, and many new and important discoveries have been made in the past decade. This First Part Part of Two CCK Volumes dealing with Unimolecular Rections, deals with the Reaction Step. The first chapter is an introduction to the whole project, aiming to cover the material necessary to understand the content of the detailed chapters, as well as the history of the development of the area. Chapter 2 is a review of the modern view of the statistical theories, as embodied in the various forms of RRKM theory. Chapter 3 deals with the fully quantum mechanical view of reactive states as resonances. . Presents considerable advances in the field made during the last decade. . Treats both the statistical as well as the fully quantum mechanical view.

Role of Active Modes in Unimolecular Reactions Volume 2 Thermal Decomposition of Fluoroform and Methane

A recently developed model has been applied to the Rice-Ramsperger-Kassel-Marcus (RRKM) theory of unimolecular reactions to calculate rate constants for the thermal decomposition of fluoroform and methane.

Role of Active Modes in Unimolecular Reactions  Volume 2  Thermal Decomposition of Fluoroform and Methane

A recently developed model has been applied to the Rice-Ramsperger-Kassel-Marcus (RRKM) theory of unimolecular reactions to calculate rate constants for the thermal decomposition of fluoroform and methane. Unlike previous failures to determine the pressure dependence for the thermal decomposition of fluoroform and methane by means of the quantum statistical RRKM theory of unimolecular reactions, the new model correlates available experimental data for both fluoroform and methane. In addition, the new model predicts a pressure dependence for the thermal decomposition of methane in the second-order region at high pressures. The latter result suggests that further experiments are required to measure the pressure dependence of the unimolecular rate constants for the thermal decomposition of methane. (Author).

Molecular Beam Studies of Unimolecular Reactions

Several methods currently used to study unimolecular decomposition in molecular beams are discussed. Experimental product angular and velocity distributions obtained for the reaction of F, Cl with C2H3Br are presented.

Molecular Beam Studies of Unimolecular Reactions

Several methods currently used to study unimolecular decomposition in molecular beams are discussed. Experimental product angular and velocity distributions obtained for the reaction of F, Cl with C2H3Br are presented. The mechanism by which conservation of angular momemtum can cause coupling of the product angular and velocity distributions in dissociation of long-lived complexes is introduced. 14 references.