Description
Ethyl cyanide, CH_3_CH_2_CN, is an important interstellar molecule with a very dense rotational-vibrational spectrum. On the basis of new laboratory data in the range of 17-605GHz and ab initio calculations, two new vibrational states, {nu}_12_ and {nu}_20_, have been detected in molecular clouds of Orion. Laboratory data consist of Stark spectroscopy (17-110GHz) and frequency-modulated spectrometers (GEM laboratory in Valladolid: 17-170, 270-360GHz; Toyama: 26-200GHz; Emory: 200-240GHz; Ohio State: 258-368GHz; and JPL: 270-318, 395-605GHz). More than 700 distinct lines of each species were measured in J up to 71 and in K_a_ up to 25. The states were fitted with Watson's S-reduction Hamiltonian. The two new states have been identified in the interstellar medium toward the Orion Nebula (Orion KL). The ground state, the isotopologues of CH_3_CH_2_CN, and the vibrationally excited states have been fitted to obtain column densities and to derive vibrational temperatures. All together, ethyl cyanide is responsible for more than 2000 lines in the observed frequency range of 80-280GHz.
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