Theory-based questions, importance

The justification of jr-electron theories has been repeatedly questioned during recent years indeed, it has become almost fashionable to emphasize the shortcomings of the cr—it separation and the non-validity of the theories based upon it. These are, in fact, approximations and cannot be expected to lead to unconditionally reliable conclusions. However, the numerical results that have provoked the criticisms in question are not a necessary consequence of the a—it separation and the related approximations. Therefore, we shall begin by restating and clarifying the basic concepts on which the whole question of the a—it separation rests. We shall consider the conditions under which the electrons of a molecule can be classified into a and it electrons and indicate what should be understood be a—7i separation and what are the limitations of this approximation. We shall show that the most important part of th e a—n interaction is usually taken into accound within the a—n separation scheme and, finally, discuss whether the a—it interaction has a significant effect on the theoretical predictions made for the physical properties of unsaturated molecules (ionization potentials, electronic spectra, charge densities and dipole moments etc.). 

The approach is ideally suited to the study of IVR on fast timescales, which is the most important primary process in imimolecular reactions. The application of high-resolution rovibrational overtone spectroscopy to this problem has been extensively demonstrated. Effective Hamiltonian analyses alone are insufficient, as has been demonstrated by explicit quantum dynamical models based on ab initio theory [95]. The fast IVR characteristic of the CH cliromophore in various molecular environments is probably the most comprehensively studied example of the kind [96] (see chapter A3.13). The importance of this question to chemical kinetics can perhaps best be illustrated with the following examples. The atom recombination reaction... 

Although many interface models have been given so far, they are too qualitative and we can hardly connect them to the mechanics and mechanism of carbon black reinforcement of rubbers. On the other hand, many kinds of theories have also been proposed to explain the phenomena, but most of them deal only with a part of the phenomena and they could not totally answer the above four questions. The author has proposed a new interface model and theory to understand the mechanics and mechanism of carbon black reinforcement of rubbers based on the finite element method (FEM) stress analysis of the filled system, in journals and a book. In the new model and theory, the importance of carbon gel (bound rubber) in carbon black reinforcement of rubbers is emphasized repeatedly. Actually, it is not too much to say that the existence of bound rubber and its changeable and deformable characters depending on the magnitude of extension are the essence of carbon black reinforcement of rubbers. 

A purely thermodynamic treatment of detonation ignores the important question of reaction time scales. The finite time scale of reaction leads to strong deviations in detonation velocities from values based on the Chapman-Jouguet theory.16 The kinetics of even simple molecules under high-pressure conditions is not well understood. 

Recapitulating, the SBM theory is based on two fundamental assumptions. The first one is that the electron relaxation (which is a motion in the electron spin space) is uncorrelated with molecular reorientation (which is a spatial motion infiuencing the dipole coupling). The second assumption is that the electron spin system is dominated hy the electronic Zeeman interaction. Other interactions lead to relaxation, which can be described in terms of the longitudinal and transverse relaxation times Tie and T g. This point will be elaborated on later. In this sense, one can call the modified Solomon Bloembergen equations a Zeeman-limit theory. The validity of both the above assumptions is questionable in many cases of practical importance. 

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