J/ApJ/500/1059 J/ApJ/500/1059 Dimethyl ether transitions frequencies P Groner S Albert E Herbst F C De Lucia Astrophys. J. 500 1059 1998 1998ApJ...500.1059G J/ApJ/499/517 : Ethylene oxide spectrum (Pan+, 1998) Atomic physics Interstellar medium ISM: molecules molecular data molecular processes radio lines: ISM Dimethyl ether (CH_3_OCH_3_) is a well-known interstellar molecule with a large abundance in hot core regions. We have measured many rotational-torsional transition lines of this molecule in the 100-550GHz frequency range using two experimental techniques: a klystron-based traditional millimeter-wave spectrometer and a new fast scan spectrometer (designated "FASSST") with a voltage-tunable backward wave oscillator. The lines arising from the ground vibrational state have been combined with previous data, mainly at lower frequencies, to form a global data set consisting of over 1600 lines that have been assigned and fitted by an effective Hamiltonian method. The spectral constants obtained from the fit allow us to predict the frequencies of almost 6000 additional lines of dimethyl ether through 600GHz.

t Torsional substates number=1 00=AA , 01=EE , 11=AE , 12=EA --- J' J' rotational quantum number --- K'a K'a rotational quantum number --- K'c K'c rotational quantum number --- J" J" rotational quantum number --- K"a K"a rotational quantum number --- K"c K"c rotational quantum number --- Freq Frequency MHz O-C Observed minus calculated frequency MHz e_Freq rms uncertainty on Freq number=2 A 0.000 in the uncertainties column signifies that the transition has been assigned but not included in the fit. Many of these are weaker, blended lines for which the measured frequency of the stronger neighbor was used to calculate the listed O - C. A total of 1626 assigned frequencies were used in the fit. MHz Source Source number=3 L: Lovas et al. 1979, J. Phys. Chem. Ref. Data 8, 1051 D: Durig et al. 1976, J. Molec. Spectrosc. 62, 159 N: Neustock et al. 1990, Z. Naturforsch. 45a, 702 K: this work, klystron-based measurements F: this work, FASSST-based measurements --- t Torsional substates number=1 Torsional substates: 00=AA , 01=EE , 11=AE , 12=EA --- J' J' rotational quantum number --- K'a K'a rotational quantum number --- K'c K'c rotational quantum number --- J" J" rotational quantum number --- K"a K"a rotational quantum number --- K"c K"c rotational quantum number --- Freq Frequency MHz e_Freq rms uncertainty on Freq MHz WSpin Spin weight --- S S value (Townes & Schawlow, 1975, Microwave Spectroscopy (New York: Dover))) --- Eu Upper state energies cm-1 James Marcout, Patricia Bauer CDS 1999Mar09 UNKNOWN UNKNOWN From ApJ electronic version J_ApJ_500_1059.xml