Theoretical and experimental studies for the interpretation of vibrational circular dichroism spectra in the CH-stretching overtone region

Two theoretical models for the interpretation of the existing data of CH-stretching overtones' vibrational circular dichroism data are presented. The first model is based on the quantum mechanical Van Vleck contact transformation theory and is applied to the full vibrational problem, the second is based on classical trajectories calculations, by which we treat a simplified three-degrees of freedom Hamiltonian. The latter allows one to derive a qualitative but efficacious picture of the behavior of coupled anharmonic oscillators. In this framework, we analyze the Poincare Surfaces of Section, and calculate the Fourier Cross Spectra of coupled CH-stretchings. Values for the harmonic frequencies and anharmonicities are derived from absorption spectra in the near infrared on partially deuterated compounds. The effect of large amplitude, low-frequency puckering or twisting modes on the ensemble of coupled CH-stretching is taken into account. Copyright 2000 Wiley-Liss, Inc.