15min:

I. MEDVEDEV, M. WINNEWISSER, F. C. DE LUCIA, E. HERBST, Department of Physics, The Ohio State University, Columbus, OH 43210; YE ENYI, R. P. A. BETTENS, Department of Chemistry, National University of Singapore, Singapore 117543.

Although most organic molecules found in interstellar clouds are unsaturated in nature, saturated and near-saturated molecules are detected in so-called ``hot-core'' sources near the sites of high-mass star formation. One such molecule of high abundance is dimethyl ether. Based on this large abundance, interstellar searches have been conducted for the next most complex ethers --- ethylmethyl ether and diethyl ether --- and tentative detections made despite the lack of data at all but the lowest frequency regions. Clearly, millimeter-wave and submillimeter-wave spectral data are necessary for the unambiguous detection of these molecules. We have recently studied the rotational-torsional spectrum of ethyl methyl ether at frequencies up to 350 GHz. In this talk, we report a new study of the rotational spectrum of diethyl ether from 75 GHz through 400 GHz recorded with the OSU ``FASSST'' spectrometer and with the MMW spectrometer (frequency range 75 to 110 GHz) located at NUS. Unlike dimethyl ether and ethylmethyl ether, the anti-anti conformer (old notation: trans-trans or TT conformer) of diethyl ether is a semi-rigid molecule, the spectrum of which can be fitted with a standard A-reduced asymmetric top Hamiltonian. Based on our results, detailed interstellar searches for this species can now be undertaken.