Intramolecular vibrational energy relaxation

Meagher J F, Chao K J, Barker J R and Rabinovitch B S 1974 Intramolecular vibrational energy relaxation. Decomposition of a series of chemically activated fluoroalkyl cyclopropanes J. Phys. Chem. 78 2535 3... 

Fig. 8. Schematic of a molecular motor activated by intramolecular vibration energy relaxation of manifold A towards the rotor part of the motor. The rotor is positioned on an axis connected to reservoir 1 kept at a temperature T. Vibration manifold A is represented here by a simple molecular spring that can be excited by light or by the inelastic effect of a tunneling current passing through the molecular spring. Without such an excitation, manifold A is statistically populated by reservoir 1. A specific choice of a molecular structure equivalent to the spring may avoid its complete thermalization, for example by filtering the thermal noise giving rise to a unidirectional rotary motion...

Botan V, Hamm P (2008) Intramolecular vibrational energy relaxation in nitrous acid (HONO). J Chem Phys 129 234511... 

Intramolecular relaxation rates have also been determined from the linewidths of CH stretch overtones.The linewidths are about 100 cm which corresponds to a lifetime for the initially prepared states of approximately 5 x 10 s. What is not known is whether this lifetime results from dephasing or true intramolecular vibrational energy relaxation. In allyl isocyanide,for which... 

It may seem inconsistent that statistical (RRKM) energy distributions can be observed at the critical configuration even though the lifetime distributions are apparent and/or intrinsic non-RRKM. However, there are two reasons why this is not the case. First, model master equation studies have shown that product energy distributions are insensitive to the rate of intramolecular vibrational energy relaxation.Second, RRKM lifetime distributions require... 

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. 

However, the chromophoies used in SD experiments imdergo small changes in the solute intramolecular potential. Fmthermore, since they are large polyatomics with many intramolecular vibrational modes, vibrational energy relaxation is expected to be very rapid. Thus, AE = AE. In all theories and in most simulations of SD, with a few exceptions, the intramolecular contribution to AE is neglected. 

Figure 2 Vibrational energy relaxation (VER) mechanisms in polyatomic molecules, (a) A polyatomic molecule loses energy to the bath (phonons). The bath has a characteristic maximum fundamental frequency D. (b) An excited vibration 2 < D decays by exciting a phonon of frequency ph = 2. (c) An excited vibration >d decays via simultaneous emission of several phonons (multiphonon emission), (d) An excited vibration 2 decays via a ladder process, exciting lower energy vibration a> and a small number of phonons, (e) Intramolecular vibrational relaxation (IVR) where 2 simultaneously excites many lower energy vibrations, (f) A vibrational cascade consisting of many steps down the vibrational ladder. The lowest energy doorway vibration decays directly by exciting phonons. (From Ref. 96.)...

This chapter is concerned with how energy deposited into a specific vibrational mode of a solute is dissipated into other modes of the solute-solvent system, and particularly with how to calculate the rates of such processes. For a polyatomic solute in a polyatomic solvent, there are many pathways for vibrational energy relaxation (VER), including intramolecular vibrational redistribution (IVR), where the energy flows solely into other vibrational modes of the solute, and those involving solvent-assisted processes, where the energy flows into vibrational, rotational, and/or translational modes of both the solute and the solvent. 

In this chapter we have reviewed the general theory of vibrational energy relaxation for a single oscillator coupled to a bath, and we have discussed the application of these results to three specific systems iodine in xenon, neat liquid oxygen, and W(CO)6 in ethane. In the first case the bath is the translations of the solute and solvent molecules, in the second case it is the translations and rotations of solute and solvent molecules, and in the third case it is the solute s other intramolecular vibrations and the translations of solute and solvent molecules. 

Recently, however, experimental studies have cast a doubt on this assumption (see Ref. 1 for a review). For example, spectroscopic studies reveal hierarchical structures in the spectra of vibrationally highly excited molecules [2]. Such structures in the spectra imply the existence of bottlenecks to intramolecular vibrational energy redistribution (IVR). Reactions involving radicals also exhibit bottlenecks to IVR [3]. Moreover, time-resolved measurements of highly excited molecules in the liquid phase show that some reactions take place before the molecules relax to equilibrium [4]. Therefore, the assumption that local equilibrium exists prior to reaction should be questioned. We seek understanding of reaction processes where the assumption does not hold. 

Y. Yamada, T. Ebata, M. Kayano, and N. Mikami, Picosecond IR-UV pump-probe spectroscopic study of the dynamics of the vibrational relaxation of jet-cooled phenol. I. Intramolecular vibrational energy redistribution of the OH and CH stretching vibrations of bare phenol, J. Chem. Phys. 120, 7400-7409 (2004). 

Single vibrational levels of the 82 state of aniline, formed by excitation within a He-aniline molecular beam, have been shown to relax in low-energy collisions with the He diluent at rates which are markedly dependent upon the identity of the vibrational mode excited. Intramolecular vibrational energy transfer within the 82 state induced by collision with HjO and CH3F is also mode specific, and rates for these processes are of the same order for these two collision partners and considerably faster than for energy transfer caused by Ar. Within p-alkylanilines, collisionless intramolecular vibrational relaxation from the initially excited NHj inversion mode to the alkyl chain modes appears to be complete within 1 ns, ... 

The above experiments reveal that two major relaxation processes must be considered for molecules inside superfluid helium droplets. These are rapid relaxation of intramolecular vibrational energy by dissipation into the helium droplet, and slow relaxation of the structural configuration of a non-superfluid helium solvation layer. At the present time the extent to which the solvation layer is involved in the energy dissipation mechanisms is not yet clear. The highly efficient coupling of the dopant to the otherwise very gentle helium environment is an effect which certainly needs to be considered in photochemical experiments performed in superfluid helium droplets. 

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