Vibrational energy exchange

Basco and Norrish25 flash photolyzed C2N2 and BrCN in the presence of NO and observed vibrationally excited nitric oxide. They suggested that it was formed through near-resonance vibration-vibration energy exchange with CN radicals and/or in the photolysis of NCNO. 

The importance of vibration-vibration exchange is now apparent in the results of the early experiments on HC1 and on hydroxyl (from H+03 - OHp+02) at pressures above 0.1 torr. These showed vibrational distributions that were nearly Boltzmann, but with shape parameters corresponding to temperatures of several thousand degrees, far greater than the translational temperatures. These distributions were samples taken after rotational relaxation and after the efficient vibration-vibration energy exchange... 

Levels above about v = 15 are populated by vibration-vibration energy exchange and, because CS is formed vibrationally excited [241] in reaction (109). 

The second method has been applied to cw CO lasers it relies on the fact that CO(t> = 0) and a number of other vibrationally cold gases preferentially deexcite lower vibrational levels of CO, where vibration-vibration energy exchange is closest to resonance [256, 257]. Consequently, controlled addition of these gases can make the populations in neighboring vibrational levels more suitable for laser action and can enhance the power output [258, 259],... 

Two cw chemical lasers have been reported that operate without any external source of power to produce atomic reagents. Cool, Shirley, and Stephens [250-252] achieved oscillation on the (00°1) —(10°0) transition of C02. The mechanism was comprised of three important stages (a) production of F atoms by the reaction NO + F2 -> NOF + F (b) reaction between F and D2 to produce DF1 (c) vibrational-vibrational energy exchange from DFf to C02 to produce C02 (00°1). Meinzer [259] was able to obtain stimulated emission from DFf itself using F atoms generated in an H2-F2 flame. 

Vibrational energy exchange between N2 and the asymmetric stretch mode of C02 [59],... 

The vibrational quanta are then redistributed over higher vibrational levels by means of v-v (vibration-vibration) energy exchanges... 

The vibrational energy exchange was accounted for by considering reactions of the following type. 

Another common feature of relaxation in benzene and R2 aniline is that a very frequent first step in the collision-induced vibrational energy exchange is endoergic up-pumping of the excited molecule, even when exoergic channels are available. The ubiquity and overall importance of this first endoergic step must be explained by any plausible mechanism for the processes observed. 

Note added in proof In view of the failure of the harmonic oscillator model to account for the observed rate of activation in unimolecular dissociation reactions (the dissociation lag problem) these calculations have been repeated for a Morse anharmonic oscillator with transition between nearest and next-nearest neighbor levels [S. K. Kim, /. Chem. Phys. (to be published)]. The numerical evaluation of the analytical results obtained by Kim has not yet been carried out. From the results obtained by us and our co-workers [Barley, Montroll, Rubin, and Shuler, /. Chem. Phys. in press)] on the relaxation of vibrational nonequilibrium distributions of a system of Morse anharmonic oscillators it seems clear, however, that the anharmonic oscillator model with weak interactions (i.e., adiabatic perturbation type matrix elements) does not constitute much of an improvement on the harmonic oscillator model in giving the observed rates of activation. The answer to tliis problem would seem to lie in a recalculation of the collisional matrix elements for translational-vibrational energy exchange which takes account of the strong interactions in highly energetic collisions which can lead to direct dissociation. 

The kinetics of plasma-chemical reactions of vibrationally excited molecnles is determined not only by their concentration but mostly by the fraction of highly excited molecnles able to dissociate or participate in endothermic chemical reactions. The formation of highly vibrationally excited molecules at elevated pressures is due not to direct electron impact but to collisional energy exchange called W relaxation. Most conventional resonant W processes usually imply vibrational energy exchange between molecules of the same kind, for example, N2(w = 1) + N2(w = 0) N2(w = 0) - - = 1), and are char-... 

Non-resonant vibrational energy exchange between molecules of a different kind is usually referred to as W exchange. Let us first consider the W exchange for diatomic molecules A and B with slightly different vibrational quanta ftcoA > Similar to W exchange of anharmonic molecules of the same kind, the adiabatic factors here also mainly determine the smallness of the probability. If a molecule A transfers a quantum (wa -f-1 m va) to a molecule B (vb + 1 vb),... 

Non-adiabatic NO synthesis proceeds through the formation and decay of the intermediate complex (see Fig. 6-6). The probability of complex formation is described by (6-24)-(6-26) decay of the complex will now be considered using the statistical theory of monomolecular reactions (Nikitin, 1970). Such an approach is acceptable because the characteristic time of vibrational energy exchange inside N20 ( S+) is much shorter than the lifetime of the complex, and vibrational-translational (VT) relaxation of N20 ( E+) is much longer than the lifetime of the complex (Rusanov, Fridman, Shohn, 1978). According to the statistical theory, the direct decomposition frequency (marked + ) of the complex N2O NO + N, and reverse decomposition frequency (marked - ) N2O N2 + O can be expressed as... 

Achasoy, O.V, Ragosin, DS. (1986), Rate Coefficients of Vibrational Energy Exchange in Laser Active Medium of CO2 Gas-Dynamic Laser with Additions of O2, H2, H2O and CO, Preprint no. 16, A.V Lykov Institute of Heat and Mass Transfer, Minsk. 

Moisan, M., Barbeau, Moreau, S., J., Pelletier, Tabrizian, M., Yahia, L.H. (2001), Int. J. Pharm., vol. 226, p. 1. Molchanov Yu.S., Starik, A.N. (1984), Kinetics of Vibrational Energy Exchange in Hydrocarbon Combustion Products during Gas Expansion in Supersonic Nozzles, Central Institute of Aviation Motors, Preprint 10160,... 

W.H. Green, J.K. Hancock, Laser excited vibrational energy exchange studies of HE, CO and NO. IEEE J. Quantum Electron. 9, 50 (1973)... 

The source terms in equations (57) characterize the variation of the vibrational level populations and atomic number densities caused by different vibrational energy exchanges and chemical reactions and are expressed via the integral opierators of slow processes ... 

It is known from experiments Gordiets et al. (1988) that in a vibrationally excited gas, near-resonant vibrational energy exchanges between molecules of the same chemical species proceed much faster than non-resonant transitions between different molecules, as well as transfers of vibrational energy to other modes and chemical reactions. Therefore the following relation between the characteristic relaxation times is fulfilled ... 

In view of the low probability of translational-vibrational energy exchange, vibrational excitation at the expense of translation of the colliding molecules and the inverse process of vibrational energy dissipation are manifested in the disper-... 

Most results on coUisional vibrational energy exchange refer either to excitation of the first vibrational level (transition v = 0 -> v = 1, Po,i) or to the reverse process of molecular deactivation (Pi,o)- However, there is only limited information on deactivation involving molecules on levels v > 1. 

Intermolecular Quasi-Resonant Vibrational Energy Exchange (Intermolecular TV Process)... 

The quasi-resonant vibrational energy exchange is particularly evident in processes like... 

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