High-resolution rovibrational analysis of vibrational states of A₂ symmetry of the dideuterated methane CH₂D₂: the levels ν₅ and ν₇ + ν₉

Abstract

The infrared spectrum of the CH₂D₂ molecule has been measured in the region 900–1500 cm⁻¹ on a Bomem DA002 Fourier transform spectrometer with a resolution of 0.0024 cm⁻¹ (FWHM, unapodized). Transitions belonging to the hot bands ν ₇ + ν₉−ν ₇, ν₇ + ν₉− ν ₉, ν₅ + ν₇−ν₅, and ν₅ + ν₉−ν₅ were extracted from the recorded spectra to determine the rovibrational energies of the A₂ symmetry vibrational states (v ₇ = v ₉ = 1) at 2329.698 cm⁻¹ and (v ₅  = 1) at 1331.409 cm⁻¹. Vibrational energies as well as rotational and centrifugal distortion parameters of the (v ₇ = v ₉=1) and (v ₅ = 1) states were determined that reproduce the experimental rovibrational energy levels of the (v ₇ = v ₉ = 1) and (v ₅ = 1) vibrational states with a d _rms deviation of 0.0017 and 0.0006 cm⁻¹, respectively. The results are discussed in relation to the equilibrium structure of methane, which is redetermined here from the experimental data, and in relation to its potential hypersurface and anharmonic vibrational dynamics.

Keywords:

• Vibrational states
• Dideuterated methane
• Rovibrational analysis
• Infrared spectroscopy
• Isotopes
• Methane structure

Acknowledgement

We enjoyed help from, and discussions with, Sieghard Albert, Fabio Mariotti and Roberto Marquardt. Our work is supported financially by the Schweizerischer Nationalfonds and ETH Zürich, including C4, CSCS and AGS.

Notes

§Visiting professor, ETH Zürich, 2004.

¶Visiting fellow, ETH Zürich, 2004.

Additional information

Notes on contributors

O. N. Ulenikov§

§Visiting professor, ETH Zürich, 2004.

E. S. Bekhtereva¶

¶Visiting fellow, ETH Zürich, 2004.