Intramolecular vibrational dynamics including rotational degrees of freedom: Chaos and quantum spectra

A criterion for chaos in quantum spectra developed by Heller et al. is applied to the vibration-rotation spectrum at about 8000 cm−1 of the X̃ 1A1 state of formaldehyde. It is found that the observed increase in complexity in the spectrum as the angular momentum quantum numbers are increased corresponds nonetheless with decreasingly stochastic behavior. This can be understood in terms of an available phase space volume that expands more rapidly than the occupied phase space volume in J increases.