Chemical reaction dynamics

Hynes J T 1985 The theory of reactions in solution Theory of Chemical Reaction Dynamics ed M Baer (Boca Raton, FL CRC Press) pp 171-234... 

The above discussion represents a necessarily brief simnnary of the aspects of chemical reaction dynamics. The theoretical focus of tliis field is concerned with the development of accurate potential energy surfaces and the calculation of scattering dynamics on these surfaces. Experimentally, much effort has been devoted to developing complementary asymptotic techniques for product characterization and frequency- and time-resolved teclmiques to study transition-state spectroscopy and dynamics. It is instructive to see what can be accomplished with all of these capabilities. Of all the benclunark reactions mentioned in section A3.7.2. the reaction F + H2 —> HE + H represents the best example of how theory and experiment can converge to yield a fairly complete picture of the dynamics of a chemical reaction. Thus, the remainder of this chapter focuses on this reaction as a case study in reaction dynamics. 

In order to segregate the theoretical issues of condensed phase effects in chemical reaction dynamics, it is usefiil to rewrite the exact classical rate constant in (A3.8.2) as [5, 6, 7, 8, 9,10 and U]... 

A completely difierent approach to scattering involves writing down an expression that can be used to obtain S directly from the wavefunction, and which is stationary with respect to small errors in die waveftmction. In this case one can obtain the scattering matrix element by variational theory. A recent review of this topic has been given by Miller [32]. There are many different expressions that give S as a ftmctional of the wavefunction and, therefore, there are many different variational theories. This section describes the Kohn variational theory, which has proven particularly useftil in many applications in chemical reaction dynamics. To keep the derivation as simple as possible, we restrict our consideration to potentials of die type plotted in figure A3.11.1(c) where the waveftmcfton vanishes in the limit of v -oo, and where the Smatrix is a scalar property so we can drop the matrix notation. 

Baer M (ed) 1985 The Theory of Chemical Reaction Dynamics (Boca Raton, FL Chemical Rubber Company)... 

Zhu I, Wdom A and Champion P M 1997 A multidimensional Landau-Zener description of chemical reaction dynamics and vibrational coherence J. Chem. Phys. 107 2859-71... 

Theory and experimental teclmiques for study of chemical reaction dynamics with ultrafast spectroscopic methods. 

The first half of this section discusses the use of the crossed beams method for the study of reactive scattering, while the second half describes the application of laser-based spectroscopic metliods, including laser-mduced fluorescence and several other laser-based optical detection teclmiques. Furtlier discussion of both non-optical and optical methods for the study of chemical reaction dynamics can be found in articles by Lee [8] and Dagdigian [9]. 

The most widely employed optical method for the study of chemical reaction dynamics has been laser-induced fluorescence. This detection scheme is schematically illustrated in the left-hand side of figure B2.3.8. A tunable laser is scanned tlnough an electronic band system of the molecule, while the fluorescence emission is detected. This maps out an action spectrum that can be used to detemiine the relative concentrations of the various vibration-rotation levels of the molecule. 

Heck A J R and Chandler D W 1995 Imaging techniques for the study of chemical reaction dynamics Ann. Rev. Phys. Chem. 46 335-72... 

Chemical reaction dynamics is an attempt to understand chemical reactions at tire level of individual quantum states. Much work has been done on isolated molecules in molecular beams, but it is unlikely tliat tliis infonnation can be used to understand condensed phase chemistry at tire same level [8]. In a batli, tire reacting solute s potential energy surface is altered by botli dynamic and static effects. The static effect is characterized by a potential of mean force. The dynamical effects are characterized by tire force-correlation fimction or tire frequency-dependent friction [8]. 

An excellent discussion of developments in chemical reaction dynamics in liquids. 

M. Baer, ed.. Theory of Chemical Reaction Dynamics Vols. I and II, CRC Press, Boca Raton, FL, 1985. 

P. J. Kuntz, Theory of Chemical Reaction Dynamics Vol I M. Baer Ed. 71, CRC Boca Ratan, EL (1985). 

J. T. Hynes, Theory of Chemical Reaction Dynamics Volume IV B. Bauer, Ed., 171, CRC, Boca Raton (1985). 

In a typical dynamic trajectory, the initial position is well controlled but the endpoint of the trajectory is unknown. For chemical reaction dynamics, we are interested in trajectories that link known initial (reactant) and final (product) states so that both the initial conditions and the final conditions of the trajectory are fixed. 

The main problem of elementary chemical reaction dynamics is to find the rate constant of the transition in the reaction complex interacting with its environment. This problem, in principle, is close to the general problem of statistical mechanics of irreversible processes (see, e.g., Blum [1981], Kubo et al. [1985]) about the relaxation of initially nonequilibrium state of a particle in the presence of a reservoir (heat bath). If the particle is coupled to the reservoir weakly enough, then the properties of the latter are fully determined by the spectral characteristics of its susceptibility coefficients. 

C. Chatgilialoglu, Advances in Chemical Reaction Dynamics, NATO ASI (Eds. P. M. Rentzepis and C. Capellos), Reidel, Amsterdam, 1986, pp. 571-579. 

Flame velocity versus fuel concentration for H2/air mixtures in the 10 m long tubes of 5, 15, and 30 cm internal diameter with obstacles (orifice plates) BR = 1 - d /D - blockage ratio, where d is the orifice diameter and D is the tube diameter. (From Lee, J.H., Advances in Chemical Reaction Dynamics, Rentzepis, P.M. and CapeUos, C., Eds., 246,1986.)... 

It is possible to propagate just the real part of a wave packet if the representation of H is real-valued, as it often is in chemical reaction dynamics. 

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