Intramolecular vibrational-energy redistribution

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. 

Callegari A, Rebstein J, Muenter J S, Jost R and Rizzo T R 1999 The spectroscopy and intramolecular vibrational energy redistribution dynamics of HOCI in the u(OH) = 6 region, probed by infrared-visible double resonance overtone excitation J. Chem. Phys. 111 123-33... 

Boyarkin O V and Rizzo T R 1996 Secondary time scales of intramolecular vibrational energy redistribution in CFgH studied by vibrational overtone spectroscopy J. Chem. Phys. 105 6285-92... 

Quasiclassical trajectory calculations are the method of choice for determining the dynamics of intramolecular vibrational energy redistribution leading to a chemical reaction. If this information is desired, an accurate reaction rate can be obtained at little extra expense. 

Another important question deals with the intramolecular and unimolecular dynamics of the X-—RY and XR -Y- complexes. The interaction between the ion and molecule in these complexes is weak, similar to the intermolecular interactions for van der Waals molecules with hydrogen-bonding interactions like the hydrogen fluoride and water dimers.16 There are only small changes in the structure and vibrational frequencies of the RY and RX molecules when they form the ion-dipole complexes. In the complex, the vibrational frequencies of the intramolecular modes of the molecule are much higher than are the vibrational frequencies of the intermolecular modes, which are formed when the ion and molecule associate. This is illustrated in Table 1, where the vibrational frequencies for CH3C1 and the Cr-CHjCl complex are compared. Because of the disparity between the frequencies for the intermolecular and intramolecular modes, intramolecular vibrational energy redistribution (IVR) between these two types of modes may be slow in the ion-dipole complex.16... 

Schwarzer D, Kutne P, Schroder C, Troe J (2004) Intramolecular vibrational energy redistribution in bridged azulene-anthracene compounds ballistic energy transport through molecular chains. J Chem Phys 121 1754... 

Reaction dynamics as opposed to reaction kinetics strives to unravel the fundamentals of reactions—just how they transpire, how intramolecular vibrational energy redistributions provide energy to the modes most involved along the reaction coordinate, how specihc reaction states progress to specihc product states, why product energy distributions and ratios of alternative products are as they are, and, of course, how fast the basic processes on an atomic scale and relevant timeframe occur. 

Another important effect on the Norrish type I/II ratio is the occurrence of intramolecular vibrational energy redistribution (IVR). For short timescale processes shorter than 10 ps (such as the Norrish type I reaction), IVR is yet far from completed as assumed by statistical theories such as RRKM. The opposite is true for Norrish type II reaction. The reaction only starts after 20 ps, pointing out that IVR seems to be necessary for the reaction. The longer the cai bon chain (the larger... 

The impact of different molecular environments and chemical substitution on timescales of intramolecular vibrational energy redistribution in aromatic molecules... 

Reaction dynamics on the femtosecond time scale are now studied in all phases of matter, including physical, chemical, and biological systems (see Fig. 1). Perhaps the most important concepts to have emerged from studies over the past 20 years are the five we summarize in Fig. 2. These concepts are fundamental to the elementary processes of chemistry—bond breaking and bond making—and are central to the nature of the dynamics of the chemical bond, specifically intramolecular vibrational-energy redistribution, reaction rates, and transition states. 

Figure 1. Intramolecular vibrational density redistribution IVR of Na3

Felker, P.M. and Zewail, A.H. (1985). Dynamics of intramolecular vibrational-energy redistribution (IVR). I. Coherence effects, J. Chem. Phys., 82, 2961-2974. 

Dynamics of intramolecular vibrational-energy redistribution (IVR). II. Excess energy dependence, ibid, 2975-2993. 

The nuclear function %a(R) is usually expanded in terms of a wave function describing the vibrational motion of the nuclei, and a rotational wave function [36, 37]. Analysis of the vibrational part of the wave function usually assumes that the vibrational motion is harmonic, such that a normal mode analysis can be applied [36, 38]. The breakdown of this approximation leads to vibrational coupling, commonly termed intramolecular vibrational energy redistribution, IVR. The rotational basis is usually taken as the rigid rotor basis [36, 38 -0]. This separation between vibrational and rotational motions neglects centrifugal and Coriolis coupling of rotation and vibration [36, 38—401. Next, we will write the wave packet prepared by the pump laser in terms of the zeroth-order BO basis as... 

As discussed in Section III, TRPES is sensitive to vibrational and rotational dynamics, as well as electronic dynamics. In this section, we give examples of the use of TRPES to the study of intramolecular vibrational energy redistribution (IVR), and the use of time-resolved PAD measurements as a probe of rotational dynamics. 

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