Molecular spectroscopy and dynamics: a polyad-based perspective

The efficiency and insight of global, polyad-based modeling in overtone spectroscopy and dynamics is demonstrated. Both vibration and vibration-rotation polyads are considered. The spectroscopic implications of polyad Hamiltonians derive from their ability to account for the detailed line positions and intensities of spectral features and their unique predictive power. The dynamical implications of polyad Hamiltonians include classical bifurcations that lead to the birth of new vibrational modes and intramolecular vibrational-rotational energy redistribution over multiple timescales. The literature is reviewed, with emphasis on acetylene results.