Vibrational energy relaxation approximations

This conceptual link between the solvent vibrational friction and vibrational energy relaxation is actually mirrored by an important practical connection. Within the rather accurate Landau-Teller approximation, (29,33,34), the rate of vibrational energy relaxation for a diatomic with frequency coq and reduced mass /i is given by... 

Coherent transport of vibrational energy is further limited by vibrational energy relaxation. Experiments on the amide I band of different peptides (NMA, apamin, scyllatoxin BPTI, and the cyclic pentapeptide) revealed a vibrational relaxation rate of approximately Ti = 1.2 ps, which is essentially independent of the particular peptide (30,53). A similar value has recently been reported for myoglobin at room temperature, with only a weak dependence of the relaxation rate on temperature down to cryogenic temperatures (140). In other words, vibrational relaxation of the amide I mode reflects an intrinsic property of the peptide group itself rather than a specific characteristic of the primary or secondary structural motifs of the... 

Equation (13.39) implies that in the bilinear coupling, the vibrational energy relaxation rate for a quantum hannonic oscillator in a quantum harmonic bath is the same as that obtained from a fully classical calculation ( a classical harmonic oscillator in a classical harmonic bath ). In contrast, the semiclassical approximation (13.27) gives an error that diverges in the limit T 0. Again, this result is specific to the bilinear coupling model and fails in models where the rate is dominated by the nonlinear part of the impurity-host interaction. 

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... 

The dynamic mechanical properties are of direct relevance to a range of unique polymer applications concerned with the isolation of vibrations or dissipation of vibrational energy in engineering components (e.g. noise reduction). Applications concerned with creep and stress relaxation under static loading conditions in engineering components can be approximately estimated from the dynamic mechanical properties determined over wide ranges of frequency and temperature. 

The production of OH described here has two features of special interest, being the only case where the vibrational energy is supplied by the electronic energy of an atom and where the proportion of energy appearing as vibration has been estimated. It appears that at least 30% of the OH radicals produced are vibrationally excited and this approximate figure is obtained on the basis that the relative proportions observed do not represent an appreciable relaxation from a state of higher excitation. This appears to be a reasonable assumption in this case, since Reaction 10 may well be faster than relaxation. 

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