Intramolecular dynamics effects

This is no longer the case when (iii) motion along the reaction patir occurs on a time scale comparable to other relaxation times of the solute or the solvent, i.e. the system is partially non-relaxed. In this situation dynamic effects have to be taken into account explicitly, such as solvent-assisted intramolecular vibrational energy redistribution (IVR) in the solute, solvent-induced electronic surface hopping, dephasing, solute-solvent energy transfer, dynamic caging, rotational relaxation, or solvent dielectric and momentum relaxation. 

The present approach has been applied to the experiment done by Nelsen et ah, [112], which is a measurement of the intramolecular electron transfer of 2,7-dinitronaphthalene in three kinds of solvents. Since the solvent dynamics effect is supposed to be unimportant in these cases, we can use the present theory within the effective ID model approach. The basic parameters are taken from the above reference except for the effective frequency. The results are shown in Fig. 26, which shows an excellent agreement with the experiment. The electronic couphng is quite strong and the perturbative treatment cannot work. The effective frequencies used are 1200, 950, and 800 cm for CH3CN, dimethylformamide (DMF), and PrCN [113]. 

To discover smaller specific effects on the intramolecular dynamics after attachment of an Ar atom to the benzene molecule, we performed lifetime measurements of single rovibronic states in the 6q band of the benzene-Ar and the benzene-84 Kr complex. No dependence of the lifetime on the J K> quantum number within one vibronic band was found [38]. This is in line with the results in the bare molecule and points to a nonradiative process in the statistical limit produced by a coupling to a quasi-continuum, for example, the triplet manifold. 

In conclusion, we have found that the intramolecular dynamics in the benzene molecule at low excess energy is not strongly influenced by the additional three vibrational degrees of freedom of the benzene-Ar complex. The coupling of the excited intramolecular modes to the low-frequency inter-molecular modes is weak. The observed 40% decrease of the lifetime of the 61 state does not depend on the individual excited rotation and points to an external heavy-atom effect as the source of the lifetime shortening observed for the same selectively excited rovibronic state. 

Recent works by Herman et al. and Field et al. have focused on molecules of the family of acetylene, in particular C2HD [112] and C2H2 (see Refs. 122 and 123 and Field et al., Intramolecular Dynamics in the Frequency Domain, this volume). These linear molecules have three stretching modes, 1, 2, and 3, and two doubly degenerate bending modes, trans 4 and cis 5. Isotopic effects appear particularly striking in the vibrational dynamics, as shown in the comparative study of the dynamics of the above isotopomers. 

The effects of intramolecular dynamics (vibration and rotation) on nuclear shielding have been observed as temperature dependence of resonance... 

Thus, intramolecular steric effects are of primary importance in determining the conformation of alkyl and aryl substituents attached to heterocyclic frameworks. The dynamic processes associated with these conformational states are also strongly dependent on the steric modifications between ground state and transition state. It can thus be inferred that a quantitative approach of steric effects can be obtained through these data. 

Then, as case study, we consider the glycine and glycyl radicals (Fig. 6.2) in solution. As mentioned above, the calculation of magnetic tensors needs to take into account the several factors such as the geometries, environmental effects, and dynamical effects (vibrational averaging from intramolecular vibrations and/or solvent librations). We use an integrated computational approach where the molecular... 

In an effort to understand the intramolecular dynamics in unimolecular dissociation. Remade and Levine [87] used an effective Hamiltonian approach that can account for different time scales associated with unimolecular reaction. In doing so, they assumed that a dense set of energy levels lies above the dissociation barrier and that the barrier is sufficiently high that the number of states from which dissociation occurs is small compared to the number of bound states. 

The time scale of ET observed in these systems falls into the time scale of solvent relaxation and of nuclear motions and the reaction will be severely influenced by these dynamics. It is also the aim of the present study to investigate the role of intermolecular interaction, namely, solvent effects to the reaction as well as the effects of inter- and intramolecular dynamics. 

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