Intramolecular vibrational-rotational energy transfer

Collision-induced intramolecular vibration-to-rotation energy transfer appears to be inefficient. The evidence for this inference comes from the study of rotational contours in the one collision-induced transition 7 0° in glyoxal. It is found that the emission from 0° has a distribution over rotational transitions that is close to the thermal distribution. But the vibration v-j in glyoxal is a torsional motion, and the axis of torsion very nearly coincides with the smallest axis of inertia of the molecule, so if collision-induced intramolecular vibra-tion-to-rotation transfer were efficient the emission from 0 should have a nonthermal distribution in the quantum number K (which describes quantization of the motion about the smallest axis of inertia). Note, however, that the collision partner used in this experiment was... 

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. 

Figure 3.10 Vibrational deexcitation of a classical Morse oscillator as a function of the orientation angle fl0 (see text), according to Kelley [98], for the case mA + mB mc = 2 + 1 - 1. Rotational energy is acquired via intramolecular V—R transfer. AirT0T is the net internal energy lost by the molecule BC.

It is instructive to examine a zeroth-order calculation of intramolecular energy transfer in a model molecule in which the energies of the vibrational and rotational modes are conserved separately, in which the initial excitation of the van der Waals stretching mode is zero (n = 0), and in which the initial values of... 

INTRAMOLECULAR dynamics is the time evolution of rotational, vibrational, and electronic degrees of freedom of isolated individual molecules, that is, molecules in a collision-free environment. As in any mechanical system, one can consider the time evolution of any of a variety of system properties. Intramolecular energy transfer focuses... 

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