Vibrational overtones of some deuterated propanes: the methylene chromophore

The CH bond stretching spectra of two propane isotopomers CD3CH2CD3 and CD3CHDCD3, have been recorded in the gas phase from 2800 to 16,000 cmK1. They exhibit strong evidence of Fermi resonance couplings with other vibrational modes of the molecule. The spectra have been reconstructed with a model Hamiltonian which takes into account the coupling of the CH stretch vibrations, described by Morse potentials, with isoenergetic combination states involving the angle deformations of the methylene chromophore. Such a modelling reproduces the overall spectral features. Introducing a weak resonance with the CC stretching modes only slightly improves the fit of the experimental spectra. q 2005 Elsevier B.V. All rights reserved.