Energy transfer vibration-rotation

As for rotational energy transfer, this was favored in colhsions that had large impact parameters. In general, impact parameters less than 0Jb were required before vibrational energy transfer could be achieved the smaller the impact parameter the greater the possible vibrational energy transfer. Pure rotational energy transfer occurred with probability at least... 

In condensed phases it is well known there are energy transfers between rotational and vibrational states. Indeed, molecular rotation does not actually occur in liquids - rotational states turn into vibrational states because of an increase in collisions. For liquids, the collision rate is dose to 10 collisions per second. Micro-wave spectroscopic studies of molecular rotation only use dilute gases to obtain pure rotational states with a suflident lifetime. Broadening of rotational transitions induced by molecular collisions occurs because pressures are dose to a few tenths of a Bar as described for Fig. 1.10. 

Since each sp)ecies at high temperatures has an mtemal energy component (vibration, rotation, electronic excitation) energy is transfere in the course of an inelastic collision when the particle becomes unexcited. This effect is taken into account by the internal thermal conductivity which is determined from the theory of... 

For more complicated reaction systems with competing reaction pathways, an additional master equation modeling is necessary to calculate and predict reaction rate coefficients. This treatment [28] includes the collisional energy transfer between rotational and vibrational energy levels of the reactants through activation or collisional deactivation and the different energy amount needed to overcome the transition states. 

In 1934, N. Semenov, in his book on chain reactions [2] strongly emphasized the role of the collisional energy transfer in gas-phase chemical kinetics, particularly paying attention to different kind of molecular energy, electronic, vibrational, rotational and translational. However, it was not until the work by Landau and Teller in 1936 [3] when it was realized that the collisional energy transfer should be described in terms of kinetics of populations of individual energy levels. Later on, the discussion of the energy transfer become indispensable sections of comprehensive texts on chemical kinetics as exemplified by the Kondratiev book [4]. 

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. 

Resonant rotational to rotational (R-R) energy transfer may have rates exceeding the Leimard-Jones collision frequency because of long-range dipole-dipole interactions in some cases. Quasiresonant vibration to rotation transfer (V-R) has recently been discussed in the framework of a simple model [57]. 

My own research efforts [4] have, for many years, involved taking into account such non-Bom-Oppen-heimer couplings, especially in cases where vibration/rotation energy transferred to electronic motions causes... 

C3.3.4 DEDUCING ENERGY TRANSFER MECHANISMS FROM POPULATION AND VELOCITY DISTRIBUTIONS OF THE SCATTERED BATH MOLECULES ROTATIONAL STATE POPULATION DISTRIBUTIONS FOR VIBRATIONAL EXCITATION OF THE BATH... 

Michaels C A, Lin Z, Mullin A S, Tapalian H C and Flynn G W 1997 Translational and rotational excitation of the C02(00°0) vibrationless state in the collisional quenching of highly vibrationally excited perfluorobenzene evidence for impulsive collisions accompanied by large energy transfers J. Chem. Phys. 106 7055-71... 

Kreutz T G and Flynn G W 1990 Analysis of translational, rotational, and vibrational energy transfer in collisions between COj and hot hydrogen atoms the three dimensional breathing ellipse model J. Chem. Phys. 93 452-65... 

Loesoh FI J and Flersehbaeh D R 1972 Ballistio meohanism for vibrational and rotational energy transfer in Ar + Csl oollisions J. Chem. Rhys. 57 2038-50... 

The use of molecular and atomic beams is especially useful in studying chemiluminescence because the results of single molecular interactions can be observed without the complications that arise from preceding or subsequent energy-transfer coUisions. Such techniques permit determination of active vibrational states in reactants, the population distributions of electronic, vibrational, and rotational excited products, energy thresholds, reaction probabihties, and scattering angles of the products (181). 

Electronic excitation from atom-transfer reactions appears to be relatively uncommon, with most such reactions producing chemiluminescence from vibrationaHy excited ground states (188—191). Examples include reactions of oxygen atoms with carbon disulfide (190), acetylene (191), or methylene (190), all of which produce emission from vibrationaHy excited carbon monoxide. When such reactions are carried out at very low pressure (13 mPa (lO " torr)), energy transfer is diminished, as with molecular beam experiments, so that the distribution of vibrational and rotational energies in the products can be discerned (189). Laser emission at 5 p.m has been obtained from the reaction of methylene and oxygen initiated by flash photolysis of a mixture of SO2, 2 2 6 (1 )-... 

Clearly, catalytic rate constants are much slower than vibrational and rotational processes that take care of energy transfer between the reacting molecules (10 s). For this reason, transition reaction rate expressions can be used to compute the reaction rate constants of the elementary reaction steps. 

SCHWENKE TRUHLAR Vibrational Rotational Energy Transfer 177... 

SCHWENKE TRUHLAR Vibrational 8 Rotational Energy Transfer 181... 

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