Fermi resonance phase space structure from experimental spectra

The method of algebraic resonance dynamics is developed to extract semiclassical dynamics of molecules from the fit to the experimental spectrum of bend and stretch normal modes with 2:1 Fermi resonance. The Heisenberg correspondence principle is used to determine phase space profiles for resonance polyads. Each quantum level in a polyad corresponds to a trajectory in action-angle phase space. Profiles for experimental spectra of CO2 and a series of substituted methanes show a common phase space structure with four distinct types of semiclassical motion.