Intramolecular dynamics experimental results

In conclusion, the method of intramolecular excimer formation is rapid and convenient, but the above discussion has shown that great care is needed for a reliable interpretation of the experimental results. In some cases it has been demonstrated that the results in terms of equivalent microviscosity are consistent with those obtained by the fluorescence polarization method (described in Section 8.5), but this is not a general rule. Nevertheless, the relative changes in fluidity and local dynamics upon an external perturbation are less dependent on the probe, and useful applications to the study of temperature or pressure effects have been reported. 

In this section we present experimental results for the lifetime of individual rovibronic states of benzene at different excess energies in the Si electronic state. In this way the dependence of the lifetime of the states on their excess energy and their rotational quantum number is studied. A general model for the underlying coupling mechanism is presented, and the influence of a van der Waals bound noble-gas atom on the intramolecular dynamics is investigated. 

There are a large number of possible nontraditional partitionings of molecules into weakly interacting subsystems or initially localized but rapidly evolving excitations. Major insights into intramolecular dynamics result when an experimental scheme capable of creating a new class of t = 0 localization is devised (e.g., Stimulated Emission Pumping, Kittrell, et al., 1981). 

For many years, CDs were considered to have rigid truncated-cone structures although this concept was incompatible with the ease of their complex formation and several experimental findings (mainly obtained by NMR technique). Recent experimental results demonstrate that the complexes, held together by weak nonbonded interactions, must be flexible not only in solution but also in the solid state. The truncated-cone structure of HP-)3-CDs became more flexible since the intramolecular hydrogen bond is broken by the hydroxylpropyl substituent. This flexibility preferably explains the improvement of complex forming ability and dynamic character of the complexes of HP- -CDs [22]. 

In Time Resolved Fluorescence (TRF) experiments, depicted schematically in Figure 12, the emission spectrum line shape changes from a peak value of AE(0) to the final AE(oo) peak of the equilibrium emission spectrum as the solvent responds to the new solute electronic state." " " Experimental results in bulk liquids show that the nonequilibrium correlation functions initially exhibit a very fast (less than 50 fs" ) inertial component, which may account for 60-80% of the total relaxation in water. This is followed by a multiexponential relaxation on the subpicosecond to picosecond timescale," corresponding to reorientation and translation of solvent molecules, or, to particular intramolecular solvent modes" " around the solute. Slower dynamics are found in more viscous liquids." ... 

Obviously the RRK theory is an over-simplification for intramolecular dynamics.However, it has been found useful in predicting unimolecular decay rates for comparison with both experimental results and other theoretical ones. Nevertheless, the observation of RRK-like decay in the present study does not demonstrate the validity for this system of any of the RRK assumptions, including the assumption of energy randomization. 

Recent results show that even after the annihilation of periodic orbits at a bifurcation there remain traces of the annihilated periodic orbits in the quantum amplitudes [50]. These so-called ghost periodic orbits have been interpreted in terms of the complex periodic orbits created when the corresponding real periodic orbits are annihilated. Such phenomena have been experimentally observed for Rydberg atoms in a magnetic field [11,51]. We shall show below that such phenomena are also important in intramolecular and dissociation dynamics. 

The knowledge of the two-minima energy surface is sufficient theoretically to determine the microscopic and static rate of reaction of a charge transfer in relation to a geometric variation of the molecule. In practice, the experimental study of the charge-transfer reactions in solution leads to a macroscopic reaction rate that characterizes the dynamics of the intramolecular motion of the solute molecule within the environment of the solvent molecules. Stochastic chemical reaction models restricted to the one-dimensional case are commonly used to establish the dynamical description. Therefore, it is of importance to recall (1) the fundamental properties of the stochastic processes under the Markov assumption that found the analysis of the unimolecular reaction dynamics and the Langevin-Fokker-Planck method, (2) the conditions of validity of the well-known Kramers results and their extension to the non-Markovian effects, and (3) the situation of a reaction in the absence of a potential barrier. 

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