Dynamic localization effects

Let us now discuss the localizing effect of the POs described above. For this purpose we use the quantum dynamical method presented at the end of Section 3, with allow the construction of wave functions highly localized along the POs. In this sense, we refer to these functions as scar wave functions . 

When addressing problems in computational chemistry, the choice of computational scheme depends on the applicability of the method (i.e. the types of atoms and/or molecules, and the type of property, that can be treated satisfactorily) and the size of the system to be investigated. In biochemical applications the method of choice - if we are interested in the dynamics and effects of temperature on an entire protein with, say, 10,000 atoms - will be to run a classical molecular dynamics (MD) simulation. The key problem then becomes that of choosing a relevant force field in which the different atomic interactions are described. If, on the other hand, we are interested in electronic and/or spectroscopic properties or explicit bond breaking and bond formation in an enzymatic active site, we must resort to a quantum chemical methodology in which electrons are treated explicitly. These phenomena are usually highly localized, and thus only involve a small number of chemical groups compared with the complete macromolecule. 

In the classical case, when the field intensity exceeds a threshold value, the electron s motion becomes chaotic and strong excitation and ionization takes place. In the quantum case instead, interference effects may lead to the suppression of the classical chaotic diffusion, the so-called quantum dynamical localization, and in order to ionize the atom, a larger field intensity is required (see Fig. 1). 

Intermolecular relaxation effects are a central issue in the interpretation of the ultraviolet photoelectron spectroscopy (UPS) of molecular solids. These relaxation effects result in several significant characteristics of UPS valence spectra, intermolecular relaxation phenomena lead to localized electron molecular-ion states, which are responsible for rigid gas-to-solid molecular spectral energy shifts, spectral line broadening, and dynamic electronic localization effects in aromatic pendant group polymers. 

Recently, interesting symmetry effects have been discovered in connection with the quantum kicked rotor (see, e.g., Dittrich and Smilansky (1991a,b), Bliimel and Smilansky (1992), Thaha et al. (1993), Thaha and Bliimel (1994)). The issue concerns the influence of symmetries and their destruction on the localization length of the quantum kicked rotor. Can these symmetry effects be observed in atomic and molecular physics We think that this issue is important and propose the search for the influence of symmetry on the localization length of dynamically localizing systems as an interesting and important topic for future research. Therefore, the purpose of this section is to sketch briefly the essence of these recent discoveries as an incentive for their application in atomic and molecular physics. 

Can we increase the efficiency of exciton transport in amphi-PIC J-aggregates We have to take into consideration a large disorder degree observed in amphi-PIC J-aggregates that leads to different localization effects which influence exciton dynamics in amphi-PIC J-aggregates [5]. One of the... 

Kim, Y., and Kirkpatrick, R. J. (1997). Na and NMR study of cation adsorption on mineral surfaces local enviromnents, dynamics, and effects of mixed cations. Geochim. Cosmochim. Acta 61, 5199—5208. 

Since the equilibrium properties of the medium are involved in determining these effects they are called static medium effects. However, there is another type of relevant phenomenon which is related to the dynamic properties of a condensed phase. Since the movement of molecules with respect to one another is required for the reaction to take place, the local viscosity of the system can also influence the rate of reaction. This property is also related to local intermolecular forces. Effects which depend on local viscosity have also been studied experimentally and are known as dynamic medium effects. 

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