Vibrational anharmonicity in dideuteromethane: A study of its infrared spectrum up to 17 000 cm-1

J. L. Duncan*, M. M. Law

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

12 Citations (Scopus)


Vibrational assignments for CH2D2 are made from a detailed study of its gas-phase infrared spectrum below 17 000 cm-1, up to six quanta of CH stretching excitation. Some 77 overtone and combination vibration levels are identified. These allow extraction of empirical values for approximately one-half of the 45 normal mode anharmonicity constants, and their comparison with recent ab initio predictions. Severe Fermi resonance perturbations at low excitation levels in both CD2 stretching manifolds preclude the direct extraction of any of the 17 associated anharmonicity constants. However, observation of seven Fermi resonance diads below 4000 cm-1 permits the accurate definition of the corresponding cubic resonance parameters, and the determination of unperturbed CD2 stretching fundamental wavenumbers. A simple local mode interpretation of the unperturbed stretching vibrational manifold in CH2D2 is attempted. This then yields the 10 corresponding normal mode CH and CD stretching anharmonicity constants consistent with the model applied.

Original languageEnglish
Pages (from-to)1445-1457
Number of pages13
JournalSpectrochimica Acta - Part A: Molecular and Biomolecular Spectroscopy
Issue number9
Publication statusPublished - Aug 1997


  • Anharmonicity constants
  • Dideuteromethane
  • Vibrational assignment


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