GLOBAL FIT OF TORSION-ROTATION TRANSITIONS OF $CD_{3}OH$ TO EXPERIMENTAL PRECISION

Author Institution: Department of Physics, University of New Brunswick; Department of Physical Sciences, University of New Brunswick; Department of Physics, University of New Brunswick, FrederictonThe global fitting work reported here for $CD_{3}OH$ is a part of our overall program of global analysis of data in the ground vibration state for methanol and its isotopomers. Our program is aimed, at: (i) achieving a global fit of all observed transitions to within assigned experimental accuracies over quantum number ranges sufficient lo test the existing one-dimensional model; so far our $CH_{3}OH, ^{13}CH_{3}OH$ and $CD_{3}OH$ and analysis have shown the model can accurately describe methanol energy levels below and immediately above the torsional barrier (ie. the levels with $\nu_{t} = 0$ and 1); (ii) obtaining fundamental molecular parameters for as many methanol isotopomers as possible in the most consistent way (i.e. by using die same computer program and including data over the same quantum number range) the results of our fits for the different isotopomers should thus provide reliable molecular parameters in a logical and consistent way for meaningful inter-comparison order to explore the physical origins and mass dependence of the constants. A global fit of reported microwave (MW), millimeter-wave (MMW),and Fourier transform far--infrared (FTFIR) spectroscopic data in the ground, and first excited torsional slates of $CD_{3}OH$ has been achieved lo within experimental accuracy for the first time. In total, 325 MW and MMW lines and 5918 FTFIR lines in the quantum number ranges $V_{t} = 0 $ and 1 (below and straddling the torsional barrier) and $J_{max} = 20$ have been successfully least-squares fitted to within the measurement uncertainties of $\pm$100 kHz for the MW and MMW lines and $\pm 6$ MHz for the FTFIR lines. The converged global fit employed 55 adjustable parameters to reach an overall, unilless standard deviation of 1.058. The parameters from the current $CD_{3}OH$ global Hi will be compared with results for $CH_{3}OH$ and $^{13}CH_{3}OH$ obtained previously. A global fit currently underway for $CH_{3}$ OD also. and preliminary results will be presented