Mono-deuterated dimethyl ether: laboratory spectrum up to 1 THz
Torsion-rotational spectrum within the vibrational ground-state for the symmetric and asymmetric conformers and first detection in IRAS 16293-2422⋆
1 Laboratoire de Physique des Lasers, Atomes et Molécules, CNRS UMR 8523, Université Lille 1, 5965 Villeneuve d’Ascq Cedex, France
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2 Université de Toulouse, UPS-OMP, IRAP, Toulouse, France
3 CNRS, Institut pour la Recherche en Astrophysique et Planétologie, 9 Av. Colonel Roche, BP 44346, 31028 Toulouse Cedex 4, France
4 UJF-Grenoble 1/CNRS-INSU, Institut de Planétologie et d’Astrophysique de Grenoble (IPAG) UMR 5274, 38041 Grenoble, France
5 Institut des Sciences Chimiques de Rennes, UMR 6226 CNRS – ENSCR, Avenue du Général Leclerc, CS 50837, 35708 Rennes Cedex 7, France
6 Department of Chemistry, University of Missouri-Kansas City, Kansas City, MO 64110-2499, USA
Received: 30 November 2012
Accepted: 25 February 2013
Context. Dimethyl ether is one of the most abundant complex organic molecules (COMs) in star-forming regions. Like other COMs, its formation process is not yet clearly established, but the relative abundances of its deuterated isotopomers may provide crucial hints in studying its chemistry and tracing the source history. The mono-deuterated species (CHDOCH) is still a relatively light molecule compared to other COMs. Its spectrum is the most intense in the THz domain in the 100–150 K temperature regime, tracing the inner parts of the low-mass star-forming region. Therefore, it is necessary to measure and assign its transitions in this range in order to be able to compute accurate predictions required by astronomical observations, in particular with the telescope operating in the submm range, such as ALMA.
Aims. We present the analysis of mono-deuterated dimethyl ether in its ground-vibrational state, based on an effective Hamiltonian for an asymmetric rotor molecules with internal rotors. The analysis covers the frequency range 150–990 GHz.
Methods. The laboratory rotational spectrum of this species was measured with a submillimeter spectrometer (50–990 GHz) using solid-state sources. For the astronomical detection, we used the IRAM 30 m telescope to observe a total range of 27 GHz, in 4 frequency bands from 100 GHz to 219 GHz.
Results. New sets of spectroscopic parameters have been determined by a least squares fit with the ERHAM code for both conformers. These parameters have permitted the first identification in space of both mono-deuterated DME isomers via detection of twenty transitions in the solar-type protostar IRAS 16293-2422 with the IRAM 30 m telescope. The DME deuteration ratio in this source appears as high as observed for methanol and formaldehyde, two species known to play an important role in the COMs formation history.
Key words: line: identification / methods: laboratory / molecular data / techniques: spectroscopic / submillimeter: ISM / ISM: molecules
Full Tables A.1, A.2, B.1, and B.2, which respectively give the measured (in laboratory) and predicted frequencies, are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (220.127.116.11) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/552/A117
© ESO, 2013