ABSTRACT
New millimeter-wave and microwave measurements for CH(3)OD have been combined with previous literature data and with an extended body of Fourier transform far-infrared observations in a full global analysis of the first two torsional states (v(t) = 0 and 1) of the ground vibrational state. The fitted CH(3)OD data set contained 564 microwave and millimeter-wave lines and 4664 far-infrared lines, representing the most recent available information in the quantum number ranges J = 20 and K = 15. A 53-parameter converged global fit was achieved with an overall weighted standard deviation of 1.060, essentially to within the assigned measurement uncertainties of +/-100 kHz for almost all of the microwave and millimeter-wave lines and +/-6 MHz for the far-infrared lines. The new parameters for CH(3)OD are compared to previous results obtained for the (12)CH(3)OH, (13)CH(3)OH, and CD(3)OH isotopomers over the same quantum number ranges using the identical fitting program. Strong asymmetry-induced coupling between the accidentally near-degenerate 0E and -1E v(t) = 0 substates is successfully modeled by the fit. Copyright 2000 Academic Press.
ABSTRACT
A global analysis of reported microwave (MW) millimeter wave (MMW), and Fourier-transform far-infrared (FTFIR) spectra of the CD3OH isotopic species of methanol has been carried out for the first two torsional states (nut = 0 below the barrier and nut = 1 straddling the barrier) of the ground vibrational state. The CD3OH data set contains 472 MW and MMW lines and 5320 FTFIR lines, representing the most recent available information in the quantum number ranges J = 20 and K = 15. The transitions have been successfully fitted to within the assigned measurement uncertainties of ±100 kHz for most of the MW and MMW lines and ±6 MHz for the FIR lines with the use of a program (I. Kleiner and M. Godefroid, private communication) based on the formalism of Herbst et al. (J. Mol. Spectrosc. 108, 42-57, 1984). A convergent global fit was achieved using 54 adjustable parameters to reach an overall weighted standard deviation of 0.966. The new parameters for CD3OH are compared with previous global fitting results for the 12CH3OH and 13CH3OH isotopomers. Copyright 1998 Academic Press.
ABSTRACT
The ground state rotational spectrum of CD3OH has been revisited in the millimeter-wave range. A total of 216 transition frequencies have been measured and assigned in the 117-179 GHz spectral range, including about 40 transitions previously reported. The spectrum was recorded at the Justus-Liebig University in Giessen, Germany using a frequency modulated millimeter-wave spectrometer. The assignments for the CD3OH transitions were predicted based on energy levels calculated using preliminary results of the global fit of microwave, millimeter-wave, and far-infrared data of Walsh et al. (Paper FC04 presented at the 52nd International Symposium of Molecular Spectroscopy, Columbus, OH, 1997). The new measurements have substantially enlarged the accurate millimeter-wave component of the data set available for the global fit and have allowed Walsh et al. to obtain significant improvement in the CD3OH molecular parameters (J. Mol. Spectrosc. 188, 85-93, 1998). The low residuals between observed and calculated frequencies highlight the quality of the global fit results. Copyright 1998 Academic Press.