trans-ethyl methyl ether:: Assignments and predictions up to 400 GHz for the vibrational-torsional ground state

Ethyl methyl ether (C2H5OCH3) has been tentatively detected in hot cores, which are quiescent high-density sources associated with regions of high-mass star formation. Up to now, the only published laboratory rotational-torsional transitions for this molecule lie at frequencies under 35 GHz. In this paper, we report the measurement and assignment of many rotational-torsional transitions of ethyl methyl ether in its vibrational-torsional ground state at frequencies through 350 GHz. A fit to experimental accuracy of over 1000 new and previously assigned transitions has allowed us to predict the frequencies of many additional transitions up to 400 GHz. The results of this work should enable astronomers to confirm the existence of ethyl methyl ether in interstellar sources.