15min:

P. GRONER, Department of Chemistry, University of Missouri - Kansas City, Kansas City, MO 64110; S. ALBERT, E. HERBST, F. C. DE LUCIA, Department of Physics, Ohio State University, Columbus, OH 43210; AND F. J. LOVAS, National Institute of Standards and Technology, Optical Technology Division, Gaithersburg, MD 20899.

An effective rotational Hamiltonian was used to analyze rotational transitions in the vibrational ground state of acetone. Microwave and mm-wave measurements from the literature were combined with new measurements between 260 and 350 GHz and with new FT microwave frequencies in a global fit of all four torsional substates. Over 500 frequencies between 8 and 350 GHz were fit for transitions involving energy levels with J up to 34 and K_a up to 10. In one (preliminary) fit, 31 spectroscopic parameters were used to fit 555 frequencies to a dimensionless standard deviation of 1.25. The parameters determined in the least-squares fit were: \rho =0.0621754(64), ß =25.8160(73) deg., parameters equivalent to the rotational, quartic and sextic distortion constants, the internal energy tunneling parameters \epsilon₀₁ =-763.436(83) MHz, \epsilon_1-1=0.1057(62) MHz, \epsilon₁₁=0.991(34) MHz, \epsilon₀₂ = 0.585(14) MHz and ten tunneling constants related to the rotational and distortion constants. This particular fit is not quite satisfactory because a number of transitions, including low K_c R-transitions, had to be excluded from the fit.