Semiclassical theory of group vibrations for linear polymer chains

The semiclassical spectral method (SSM), which employs molecular dynamics and spectral estimators to determine transition frequencies between quantum energy levels in molecular and atomic systems, is extended to include calculations for linear polymer chains. Average differences between harmonic and transition frequencies for the symmetric and asymmetric stretch modes of polyethylene are reported to be around 50 cm⁻¹ with smaller average frequency shifts for the other group vibration dispersion curves for a certain potential surface describing the macromolecule.