Dimethyl ether (CH 3 OCH 3 ) is one of the largest organic molecules detected in the interstellar medium. As an asymmetric top molecule with two methyl groups which undergo large amplitude motions and a dipole moment of μ = 1.3 D, it conveys a dense spectrum throughout the terahertz region and contributes to the spectral line confusion in astronomical observations at these frequencies. In this paper, we present rotational spectra of dimethyl ether in its ground vibrational states, which have

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... n measured in the laboratory and analyzed covering frequencies up to 2.1 THz. The analysis is based on an effective Hamiltonian for a symmetric two-top rotor and includes experimental data published so far. Frequency predictions are presented up to 2.5 THz for astronomical applications with accuracies better than 1 MHz.