SEMICLASSICAL THEORY OF GROUP VIBRATIONS FOR LINEAR POLYMER-CHAINS

The semiclassical spectral method (SSM), which employs molecular dynam ics and spectral estimators to determine transition frequencies betwee n quantum energy levels in molecular and atomic systems, is extended t o include calculations for linear polymer chains. Average differences between harmonic and transition frequencies for the symmetric and asym metric stretch modes of polyethylene are reported to be around 50 cm-1 with smaller average frequency shifts for the other group vibration d ispersion curves for a certain potential surface describing the macrom olecule.