The Application of Spectral Measures to the Stimulated Emission Pumping of Acetylene
The analysis of spectroscopic data for the signature of classically chaotic motion is of current interest1–10. Nuclear spectroscopy11,12 and computational studies13,14 have tended to emphasize the level spacing statistics involving primarily the short range level correlations. Here we discuss a complementary aspect, that of the statistics of the intensity distribution. This requires sufficient resolution to distinguish adjacent independent lines and a well established base line so that weak transitions can be discerned. So far, these conditions could only be met for computationally generated spectra. Stimulated Emission Pumping1 (SEP) is a double resonance technique which eliminates rotational congestion, yet for a given intermediate state one can access into very many highly vibrationally excited final states. Since such states are strongly mixed, it might appear that the transition intensities will vary in a smooth manner. In particular, such may be the case when a “bright” zero order state (i.e., a wave function carrying oscillator strength with respect to the intermediate level) is distributed amongst many final states. On the other hand, when good quantum numbers can be assigned, neighboring states can have quite different character and the spectral intensity can rapidly vary as a function of energy. The extent of fluctuation of intensities (with respect to their smooth envelope) can thus serve as a diagnostic for the onset of extensive state mixing and the resulting “intensity-sharing” amongst many states. One can argue however that even in the chaotic regime the fluctuations do not die out but settle to a universal limit3.
KeywordsIntensity Fluctuation Level Spacing Bright State Gaussian Ensemble Gateway State
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