theories of molecular reaction dynamics - the microscopic foundation of chemical kinetics

[...]... potential The main objectives of molecular reaction dynamics may be briefly summarized by the following points: • the microscopic foundation of chemical kinetics; • state-to-state chemistry and chemistry in real time; • control of chemical reactions at the microscopic level Before we go on and discuss these objectives in more detail, it might be appropriate to consider the relation between molecular reaction. .. independent of the size of the system), PA and d2 σR /(dvC dΩ) must therefore also be intensive properties independent of the beam geometries The differential cross-section is a function of the quantum states (ijl), the relative speed v = |vA − vB | of the reactants, and the continuous velocity of the product, specified by the space angle Ω and the speed vC Since it is an intensive property of the chemical reaction, ... that on the left-hand side of the vertical bar in the argument list we have written the quantum numbers and the relative speed that specifies the state of the reactants, whereas the quantum numbers and velocities on the right-hand side specify the state of the products The notation |m,vD implies that the number of C molecules in the specified state is counted only when D is in the state m, vD The complete... elementary reactions and together they constitute what is called the reaction mechanism of the reaction It is a great challenge in chemical kinetics to discover the reaction mechanism, that is, to unravel which elementary reactions are involved Elementary reactions are reactions that directly express basic chemical events, that is, the making or breaking of chemical bonds In the gas phase, there are... for the collision energies and over the internal quantum states of the reactants A parameter in the equilibrium Boltzmann distribution is the macroscopic temperature T Under such conditions the well-known rate constant k(T ) of chemical kinetics can be defined and evaluated based on the underlying detailed dynamics of the reaction The macroscopic rate of reaction is, typically, much slower than the. .. such conditions the stateto-state dynamics described above cannot be studied, and the focus is then turned to the evaluation of the rate constant k(T ) for elementary reactions The elementary reactions in a solvent include both unimolecular and bimolecular reactions as in the gas phase and, in addition, bimolecular association/recombination reactions That is, an elementary reaction of the type A + BC... Introduction Chemical reactions, the transformation of matter at the atomic level, are distinctive features of chemistry They include a series of basic processes from the transfer of single electrons or protons to the transfer of groups of nuclei and electrons between molecules, that is, the breaking and formation of chemical bonds These processes are of fundamental importance to all aspects of life in the. .. enable a calculation of the rate of the reaction It does not provide direct insight into the process at a microscopic molecular level The aim of molecular reaction dynamics is to provide such insight as well as to deduce rate laws and calculate rate constants from basic molecular properties and dynamics Dynamics is in this context the description of atomic motion under the influence of a force or, equivalently,... place in the gas phase (in a single elementary reaction step), e.g., in the form of so-called radiative recombination; see Section 6.5 Nuclear dynamics: the Schr¨dinger equation o 5 pulse’ The first femtosecond pulse initiates a chemical reaction, say the breaking of a chemical bond in a unimolecular reaction, and a second time-delayed femtosecond pulse probe this process The ultrashort duration of the. .. established The outcome of an isolated (microscopic) reactive scattering event can be specified in terms of an intrinsic fundamental quantity: the reaction cross-section The cross-section is an effective area that the reactants present to each other in the scattering process It depends on the quantum states of the molecules as well as the relative speed of the reactants, and it can be calculated from the collision . y0 w0 h1" alt="" Theories of Molecular Reaction Dynamics This page intentionally left blank Theories of Molecular Reaction Dynamics The Microscopic Foundation of Chemical Kinetics Niels Engholm. Chapter 4 is the longest chapter of the book with the focus on the key issue of the nuclear dynamics of bimolecular reactions. The dynamics is described by the quasi-classical approach as well as. we turn to the other basic type of elementary reaction, i.e., uni- molecular reactions, and discuss detailed reaction dynamics as well as transition-state theory for unimolecular reactions. In