Abstract
Stimulated-emission pumping spectra of acetylene- for J″ ≤ 10 and l″ (≈Ka) = 0, 2 at 11 400–15 700 cm−1 above the zero-point level exhibit a puzzling combination of contradictory symptoms of both regularity and severe mixing. The stimulated-emission pumping spectra are subjected to a variety of analyses in order to characterize the extent of vibrational mixing and the separability of rotation and vibration. These schemes include reduced term-value plots (from which 31 subband origins and B values were derived), screening for coincidences between term values accessible from successive upper-state (Ã1Au) rotational levels, polarization diagnostics, comparisons between observed, calculated total, and calculated Franck–Condon permitted vibrational densities of states, and various types of level-spacing statistics that are frequently used in studies of the quantum analog of classical chaos. The most remarkable observations are (i) the profound difference between the properties of l″ = 0 versus l″ = 2 levels, in particular the persistence of relatively perturbation-free term value plots for l″ = 0 levels but not for l″ = 2 levels, (ii) the negligibly small parity doubling of l″ = 2 levels, (iii) evidence of vibrational mixing (but not l″ mixing) within both l″ = 0 and l″ = 2 submanifolds, and (iv) nearly Poisson fluctuations of the level spacings rather than the spectral rigidity that underlies some forms of extremely chaotic classical dynamics.
© 1990 Optical Society of America
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