On the Detection of Dimethyl Ether, (CH3)2O, in the ISM

L. E. Snyder, D. Buhl, P. R. Schwartz, F. O. Clark, D. R. Johnson, F. J. Lovas, and P. T. Giguere,
reported on the Radio Detection of Interstellar Dimethyl Ether
Astrophys. J. 191, L79–L82 (1974).
The 21,1 – 20,2 transition near 1 cm and the 22,0 – 21,1 and 60,6 – 51,5 transitions in the 3 mm region were detected toward Orion A employing the 11 m telecope of the NRAO.

The molecules is not only very abundant in hot cores, but it has also been detected toward a low-mass proto-star fairly recently:
S. Cazaux, A. G. G. M. Tielens, C. Ceccarelli, A. Castets, V. Wakelam, E. Caux, B. Parise, D. Teyssier,
The Hot Core around the Low-mass Protostar IRAS 16293-2422: Scoundrels Rule!
Astrophys. J. 593, L51–L55 (2003).

The molecule was also detected in some of the investigated Galactic center molecular clouds which have low dust temperatures (10–20 K), even lower rotational temperatures (around 10 K), which are moderately dense (a few tenthousand molecules per cubic centimeter), but which are kinetically moderately warm (about 100 K or more). Two transitions were detected with the IRAM 30 m telescope in the 3 mm range by
M. A. Requena-Torres, J. Martín-Pintado, A. Rodríguez-Franco, S. Martín, N. J. Rodríguez-Fernández, and P. de Vicente,
Organic Molecules in the Galactic Center – Hot Core Chemistry without Hot Cores
Astron. Astrophys. 455, 971–985 (2006).
The column density relative to methanol is reasonable. Considering also the low rotational temperature, the detection is probably fairly secure, even though only two transitions were detected.

C. Richard, L. Margulès, E. Caux, C. Kahane, C. Ceccarelli, J.-C. Guillemin, R. A. Motiyenko, C. Vastel, and P. Groner
reported on
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
Astron. Astrophys. 552, Art. No. A117 (2013).
Four frequency windows between 100 and 220 GHz were observed with the IRAM 30 m single dish telescope. Four transitions of the symmetric conformer as well as six transitions of the asymmetric conformer were detected. Non of the transitions showed torsional splitting. The only one, which was expected to show such splitting, was overlapped. It was one of the four transitions of the symmetric conformer. The high degree of deuteration (about 15 %) suggests that doubly deuterated isotopologs may be detectable at least with ALMA or other interferometers.

S. E. Bisschop, P. Schilke, F. Wyrowski, A. Belloche, C. Brinch, C. P. Endres, R. Güsten, H. Hafok, S. Heyminck, J. K. Jørgensen, H. S. P. Müller, K. M. Menten, R. Rolffs, and S. Schlemmer,
reported on
Dimethyl Ether in its Ground State, v = 0, and Lowest Two Torsionally Excited States, v11 = 1 and v15 = 1, in the High-mass Star-forming Region G327.3-0.6
Astron. Astrophys. 552, Art. No. A122 (2013).
A plethora of rotational transitions have been detected with the APEX 12 m single dish telescope in the course of a line survey covering frequencies in the 1.3, 1.0, 0.9, 0.43, and 0.37 mm wavelength regions. The vibrations are at about 200 and 240 cm–1, respectively. Much higher vibrational states will be observable with interferometers such as ALMA. No evidence was found for (far-) infrared pumping.

M. Koerber, S. E. Bisschop, C. P. Endres, M. Kleshcheva, R. W. H. Pohl, A. Klein, F. Lewen, and S. Schlemmer,
reported on
Laboratory Rotational Spectra of the Dimethyl Ether 13C-Isotopologues up to 1.5 THz
Astron. Astrophys. 558, Art. No. A112 (2013).
The authors also gave a brief account on the detection of the singly substituted species in the high-mass star-forming region G327.3-0.6 within the molecular line survey mention in the previous paragraph.


Contributor(s): H. S. P. Müller; 10, 2010; 07, 2012; 05, 2013; 11, 2014