Simultaneous Rovibrational Analysis of the ν₂, ν₃, ν₅, and ν₆ Bands of H₃¹²CF

Author： Papoušek D. Pracna P. Winnewisser M. Klee S. Demaison J.

ISSN： 0022-2852

Source： Journal of Molecular Spectroscopy, Vol.196, Iss.2, 1999-08, pp. : 319-323

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Abstract

A total of 4892 transition wavenumbers of the ν₂, ν₃, ν₅, and ν₆ fundamental bands of H₃¹²CF and 1469 frequencies of the rotational transitions in the v₂ = 1, v₃ = 1, v₅ = 1, and v₆ = 1 vibrational states have been fitted simultaneously by taking explicitly into account various Coriolis interactions, l-type interactions, and α-resonance terms between and within the vibrational states. The standard deviation of the fit using 71 parameters was 8.10 × 10^-5 cm^-1 for the infrared data and 0.198 MHz for the rotational data. This study clearly shows that in order to obtain a really quantitative fit of the highly precise data of vibration–rotational and rotational spectroscopy, it is necessary to fit all the data simultaneously using a variational approach. The deperturbed values of the upper state rotational constants differ significantly from those obtained previously in fitting the ν₃ and ν₆ bands as isolated bands and the ν₂/ν₅ bands by a variational approach. This is important for the precise determination of the equilibrium structure of methyl fluoride (J. Demaison, J. Breidung, W. Thiel, and D. Papoušek, Struct. Chem., in press). Besides this, the results can be used in further studies of the reduced Hamiltonians for more complicated systems of interacting vibrational levels.