Internal vibrational energy

Once prepared in S q witli well defined energy E, donor molecules will begin to collide witli batli molecules B at a rate detennined by tire batli-gas pressure. A typical process of tliis type is tire collision between a CgFg molecule witli approximately 5 eV (40 000 cm or 460 kJ mor ) of internal vibrational energy and a CO2 molecule in its ground vibrationless state 00 0 to produce CO2 in tire first asymmetric stretch vibrational level 00 1 [11,12 and 13]. This collision results in tire loss of approximately AE= 2349 cnA of internal energy from tire CgFg,... 

Figure C3.3.4. A schematic diagram of an apparatus described in the text for studying vibrational energy transfer to small bath molecules from donor molecules having chemically significant amounts of internal vibrational energy.

A and B is converted to the internal (vibrational) energy of the association product. By analogy, the highly excited species formed is denoted C. Because it is highly unstable, C may unimolecularly dissociate by the forward direction of reaction 9.101, with rate constant kd, or if C collides with another species M, it could be stabilized via the reverse of reaction 9.100, forming the product C. 

The fraction of molecules with a total internal vibrational energy e (i.e., with n vibrational quanta among the s vibrational modes) is found from Eqs. 10.114 and 10.115 to... 

Molecules A and B react to form the excited (energized) reactive intermediate species C (n) in reaction 10.178. Translational energy of the reactant molecules from their relative motion before collision is converted to internal vibrational energy of C (n). The rate constant for formation of C (n) is assumed to depend on n and the temperature T. The forward rate constant is written as ka,oof(n, T) a constant term times a to-be-determined function f(n, T). This function is the probability of forming C (n) in a given energy state n at some temperature T it is normalized as... 

Other endoergic reactions for which an increased cross section has been observed when the internal vibrational energy of the ionic reactant... 

The effect of reactant internal vibrational energy on molecular fragment ion ratios resulting from dissociative charge transfer of some large alkanes has also been accurately predicted by the QET.476... 

For polyatomic gases that have internal vibrational energy, Eucken has suggested a semiempirical formula for a which seems to fit the data fairly well ... 

As another example consider the internal vibrational energy of a diatomic solute molecule, for example, CO, in a simple atomic solvent (e.g. Ar). This energy can be monitored by spectroscopic methods, and we can follow processes such as thermal (or optical) excitation and relaxation, energy transfer, and energy migration. The observable of interest may be the time evolution of the average... 

Most of the earlier theoretical studies dealt with the simplest relaxation mechanism where the internal vibrational energy of the guest is dissipated directly into the delocalized and harmonic lattice phonons. The common results of these works " were, as we mentioned above, predictions of a strong temperature dependence for the relaxation and an exponential decrease in the rates with the size of the vibrational frequency. The former result has its origin in stimulated phonon emission the conversion of vibrational energy into lattice phonons is greatly facilitated if some excited phonon states are thermally populated. The energy-gap law is due to the fact that the order of the multiphonon relaxation increases with the size of... 

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