ROTATIONAL ANALYSIS OF THE VIBRATIONAL GROUND STATE OF DIMETHYL ETHER, $CH_{3}$ $OCH_{3}$

$^{m}$P. Groner, submitted. $^{n}$F. J. Lovas, H Lutz and H. Dreizler, J. Phys. Chem. Ref. Data (1979) 8, 1057-1107; J. R. During, Y.S. LI and P. Groner, J. Mol, Spectrose. (1976)62, 159--174 $^{o}$W. Neustock A. Guarnicri. J. Demaison and G. Wlodarczak, Z. Naturforsch, Part A (1990) 45m 702, 702--706.Author Institution: Department of Chemistry, University of Missouri; Department of Physics, Ohio State UniversityAn effective rotational $Hamiltonian^{m}$ was used to analyse the rotational transitions in the vibrational ground state of dimethyl ether. $Microwave^{n}$ and mm-$wave^{o}$ measurements from the literature were combined with new measurements between 100 and 550 GHz in a global fit of all four torsional substates. Frequencies between 8 and 550 GHz were fit for transitions involving energy levels with {J} up to 40 and $K_{a}$ up to 9. Only 22 spectroscopic parameters were necessary to fit 1499 frequencies to experimental precision (dimensionless standard deviation 0.67), The following parameters were determined in the least-squares fit: $\rho = 0.21665 (19) \beta $= 8.426(27) deg., parameters equivalent to the rotational, quartic and sextic distortion constants the internal energy tunneling parameters $\epsilon_{01} = -3.0392(43)$ MHz and $\epsilon_{02} = 0.0019(17)$ MHz and three tunneling constants related to the ``rotational” constants