Scattering, reactive product analysis

The quantization of transition state energy levels is not simply a mathematical device to add quantum effects to the partition functions. The quantized levels actually show up as structure in the exact quantum mechanical rate constants as functions of total energy [51]. The interpretation of this structure provides clear evidence for quantized dynamical bottlenecks, both near to and distant from the saddle points, as reviewed elsewhere [52]. Quantized variational transition states have also been observed in molecular beam scattering experiments [53]. Analysis of the reactive flux in state-to-state terms from reactant states to transition state levels to product states provides the ultimate limit of resolution allowed by quantum mechanics [53,54]. Quantized energy levels of the variational transition state have been used to rederive TST using the language of quantum mechanical resonance scattering theory [55]. 

Key topics covered in the review are the analysis of the wavepacket in the exit channel to yield product quantum state distributions, photofragmentation T matrix elements, state-to-state S matrices, and the real wavepacket method, which we have applied only to reactive scattering calculations. 

As in M + X2, the reactive scattering is strongly anisotropic, but now the diatomic product is found predominantly in the backward hemisphere. The early experiments [2,43, 70], performed without velocity selection or velocity analysis, were difficult to interpret quantitatively because of the unfavorable kinematics, which arose because (a) mKI mcH, (b) considerable blurring was introduced by the spread in the incident velocities, and (c) the v lu f factor in the Jacobian distorts the lab distribution and cannot be... 

In this paper, we will present a detailed analysis of the way In which resonances may affect the angular distribution of the products of reactive collisions. To do this, we have used an approximate three-dimensional (3D) quantum theory of reactive scattering (the Bending-Corrected Rotating Linear Model, or BCRLM) to generate the detailed scattering Information (S matrices) needed to compute the angular distribution of reaction products. We also employ a variety of tools, notably lifetime matrix analysis, to characterize the Importance of a resonance mechanism to the dynamics of reactions. 

Fig. 1. Alkali atom reactive scattering apparatus incorporating a compact selector /or product velocity analysis.

Tn the early 1950s, when Taylor and Datz (I) were planning their pioneering crossed molecular beam reactive scattering experiments, they planned to use neutron activation analysis to measure the angular distribution of condensed product KBr molecules formed in Reaction 1... 

One of the main tools that lead to the highly improved understanding of photodissociation dynamics in the recent years is the analysis of the characteristic motion of the products. The analysis of the characteristic motion in the products leads to a microscopic understanding of photodissociation processes, because it contains very detailed information about the interaction. It is the same method that is used to understand other dynamical processes like chemical reactions, inelastic collisions or surface scattering. In the case of reactive collisions it led to a microscopic understanding of chemical reactions and to the Nobel prize in chemistry for Lee, Herschbach and Polanyi in I986. 

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