SIMBAD references

The torsional Raman spectra of two astrophysically detected isotopologues of dimethyl ether (DME, ¹²CH₃O¹²CH₃ and ¹³CH₃O¹²CH₃) have been recorded at room temperature and cooled in a supersonic jet and interpreted with the help of highly correlated ab initio calculations. DME displays excited torsional and vibrational levels at low energy that can be populated at the temperatures of the star-forming regions, obliging to extend the analysis of the rotational spectrum over the ground state. Its spectrum in the THz region is rather complex due to the coupling of the torsional overtones 2ν₁₁ and 2ν₁₅ with the COC-bending mode and the presence of many hot bands. The torsional overtones are set here at 2ν₁₁ = 385.2 cm^–1 and 2ν₁₅ = 482.0 cm^–1 for ¹²CH₃O¹²CH₃ and 2ν₁₁ = 385.0 cm^–1 and 2ν₁₅ = 481.1 cm^–1 for ¹³CH₃O¹²CH₃. The new assignment of 2ν₁₁ is downshifted around ∼10 cm^–1 with respect to the literature. All the other (hot) bands have been reassigned consistently. In addition, the infrared-forbidden torsional fundamental band ν₁₁ is observed here at 197.8 cm^–1. The new spectral characterization in the THz region reported here provides improved values of the Hamiltonian parameters to be used in the analysis of the rotational spectra of DME isotopologues for further astrophysical detections.