Quantum beat recurrences

Figure 7. CARS intensity versus delay time. The pulse shapes are gaussian with time constant a = 0.5 psec. 1VR is that of a two-level system (N = 2) resulting in quantum beats with complete and regular recurrences. The coupling parameter, v = 0.75ft psec"1.

The rotational temperature of 10 K in the molecular beam leads to rotational quantum numbers in the range of 10 to 20. Using the rotational constants given by Ernst and Rakowsky [70], rotational periods are estimated to be several hundreds of picoseconds. Consequently, rotational recurrences, which might interfere with the observed vibrational beat structure, appear for the first time after more than 1 ns. Therefore, the influence of the rotational motion can be neglected in the simulation, as we concentrate on the dynamics up to a few picoseconds. 

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