Vibrogram recurrences

The experimental vibrogram shows an important recurrence around 160 fs, which may be assigned to the edge periodic orbit (3,2°, -)n0rmai- Recently, the vibrogram analysis has been carried out by Michaille et al. [113] on the basis of another model proposed by Joyeux [118] as well as on an ab initio potential fitted to the experimental data of Pique [119]. Essentially the same classical periodic orbits appear in the different models at low energies. In the same context, let us add that Joyeux has recently applied the Berry-Tabor trace formula to a IF Fermi-resonance Hamiltonian model of CS2 [120] and carried out a classical analysis of several related resonance Hamiltonians [121]. 

The vibrogram has also been obtained by Jost and co-workers in the region of 12,000-15,000 cm 1, where the vibrational spectrum is irregular [111]. The main recurrence occurs at 47 fs and multiples thereof and corresponds to the bending frequency of about 714 cm-1. Thus, the spectrum is dominated by the bending motion in this regime of N02. 

Recurrences of Vibrogram of C2HD and Their Periodic-Orbit Assignment [112]... 

The vibrogram analysis [108] based on the dispersion fluorescence spectrum of acetylene by Solina et al. [125] reveals a recurrence around 50 fs from 0 to 12,000 cm"1, which is similar to the one in the previous analysis. However, an important recurrence appears at 70 fs at higher energies from 4000 to 16,000 cm 1, which is caused either by anharmonic period lengthening or by a transition to a slower regime at higher energies. 

Let us compare these results with the experimental data on CO2. A photoabsorption spectrum of CO2 has been recorded in 1965 by Nakata et al. [156]. The vibrogram as well as direct Fourier transforms of the intense band under discussion reveal main time recurrences around 50 and 60 fs [14]. On the other hand, the above model shows periods corresponding to 0 and 01 or 02 around 40 and 60 fs, respectively. Although there is a qualitative agree-... 

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