Vibrational energy flow

The existence of the polyad number as a bottleneck to energy flow on short time scales is potentially important for efforts to control molecnlar reactivity rising advanced laser techniqnes, discussed below in section Al.2.20. Efforts at control seek to intervene in the molecnlar dynamics to prevent the effects of widespread vibrational energy flow, the presence of which is one of the key assumptions of Rice-Ramsperger-Kassel-Marcns (RRKM) and other theories of reaction dynamics [6]. 

Weitz E and Flynn G W 1981 Vibrational energy flow in the ground electronic states of polyatomic molecules Adv. Chem. Rhys. 47 185-235... 

Nesbitt D J and Field R W 1996 Vibrational energy flow in highly excited molecules role of intramolecular vibrational redistribution J. Rhys. Chem. 100 12 735-56... 

Bigwood R, Gruebele M, Leitner D M and Wolynes P G 1998 The vibrational energy flow transition in organic molecules theory meets experiment Proc. Nati Acad. Sc/. 95 5960... 

Figure C3.5.11. IR-Raman measurements of vibrational energy flow tlirough acetonitrile in a neat liquid at 300 K, adapted from [41], An ultrashort mid-IR pulse pumps the C-H stretch, which decays in 3 ps. Only 1% of the energy is transferred to the C N stretch, which has an 80 ps lifetime. Most of the energy is transferred to the C-H bend plus about four quanta of C-C=N bend. The daughter C-H bend vibration relaxes by exciting the C-C stretch. The build-up of energy in the C-C=N bend mirrors the build-up of energy in the bath, which continues for about 250 ps after C-H stretch pumping.

Y. Yamada, Y. Katsumoto, and T. Ebata, Picosecond IR UV pump probe spectroscopic study on the vibrational energy flow in isolated molecules and clusters. Phys. Chem. Chem. Phys. 10, 1170 1185 (2007). 

Direct Observation of Nonchaotic Multilevel Vibrational Energy Flow in Isolated Polyatomic Molecules, P. M. Felker and A. H. Zewail, Phys. Rev. Lett. 53, 501 (1984). 

Holme TA, Hutchinson JS, Vibrational energy flow into a reactive coordinate A theoretical prototype for a chemical system J Chem Phys, 83, 2860-2869 (1985)... 

Raman spectra are specific fingerprints for individual chemical species. Clear assignments can often be made if several species are present. The Stokes and anti-Stokes intensities are compared for the determination of the vibrational population ratios and vibrational energy flow on a time-resolved basis. Isotopic Raman spectra provide information on normal modes, geometry, and chemical bonding. Molecular distortions due to solvation changes can sometimes be observed in lineshape and position changes. 

The transfer and storage of vibrational energy in large and small molecules mediate a variety of molecular processes. A central motivation for the study of vibrational energy flow in molecules has long been its influence on chemical reaction kinetics in gas and condensed phases [1-11], as well as its role in... 

Our aim is to describe the extent and rate of vibrational energy flow in molecules with perhaps tens of vibrational modes. We do this within the framework of an... 

The rate of vibrational energy flow in the reactant and product conformer is influenced by the rate of collisions with the solvent environment. Using a strong collision model, the microcanonical rate is still given by k(E) = K(E)kKKKM(E), where the IVR rate that enters into the transmission coefficient in Eq. (9) incorporates a collision frequency, a ... 

We have explored in this chapter how quantum mechanical energy flow in moderate-sized to large molecules influences kinetics of unimolecular reactions and thermal conduction. In the first part of this chapter we addressed vibrational energy flow in moderate-sized molecules, and we also discussed its influence on kinetics of conformational isomerization. In the second part we examined the dynamics of vibrational energy flow through clusters of water molecules and through proteins, and we computed thermal transport coefficients for these objects. 

For moderate-sized molecules with tens of vibrational modes, vibrational energy flow is conveniently described in a vibrational quantum number space. A statistical theory for the vibrational Hamiltonian, called Local Random Matrix Theory (LRMT), exploits the local coupling in the state space. LRMT predicts... 

Figure 29.10 shows time-profiles of the TFD-IR signal intensity at positions A-C on the TFD-IR image in Figure 29.9. As can be seen, all of the time-profiles show the same behavior. An interesting feature is that the vibrational energy of Rhodamine-6G is not completely lost, even at a 50 ps delay time, which is sufficiently longer than the fast vibrational energy flow with an exponential decay constant of 1.5 ps.

Many previous reports [34-44] on the relaxation dynamics of vibrational energy in molecules of a similar size have shown that vibrational energy flows from a solute to solvent molecules on a picosecond time scale, and is completely lost after typically 20 ps in most solutions. This suggests that the vibrational relaxation dynamics in... 

The information from such experiments, of which there are now many examples(2,3), is important to our understanding of both dynamics and structure. First, since the dynamics of the initially excited state are reflected in spectral line widths, factors which control the rate of vibrational energy flow within molecules can be studied by recording spectra as a function of molecular structure. Fast randomization of this energy is a postulate of statistical unimolecular rate theories. On the... 

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