Anharmonic coupling multiple oscillators

The origin of these multiple temperature effects lies in the dependence of the kinetic rate constants on only the translational (or more generally the bath ) temperature. For vibrational states, these results were first derived for diatomic anharmonic oscillators and used to explain laser action in CO via anharmonic pumping. Multiple vibrational temperature concepts were later applied to the polyatomic molecule SF to explain discrepancies between relaxation rates measured by ultrasonic and laser techniques. The close correspondence between the temperature picture for vibrational levels weakly coupled to a thermal bath and that for nuclear or electron spin levels also weakly coupled to a thermal bath will be immediately obvious to those familiar with spin temperature concepts. ... 

The vibrational spectra S co) after the second pulse in the cases of t = 134 and 201 fs are shown in Fig. 7.8, which clearly indicate that the amplitude of the hg(l) mode is enhanced for t = 134 fs and the predominant mode is switched to the ag(l) mode for t = 201 fs. In short, a Raman active mode is strongly excited if r is chosen to equal an integer multiple of its vibrational period TVib, and the energy of the mode takes the minimum if x is equal to a half-integer multiple of Tvib. This is known to be valid for the harmonic oscillator model. We proved that this is also the case for the potential surface of highly excited Ceo which includes anharmonic mode couplings by nature. 

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