Analysis of the terahertz rotational spectrum of the three mono-13C ethyl cyanides (13C–CH3CH2CN)

摘要

Context. Millimeter- and submillimeter-wave spectra of regions such as the Orion molecular cloud show many rotational-torsional lines that are caused by the emission of complex organic molecules (COM). Previous laboratory investigations have been conducted for three isotopologues of ethyl cyanide up to?360?GHz, and subsequently, several hundred lines of the three isotopologues have been detected in Orion?IRc2 using the IRAM?30?m radiotelescope. Aims. In this survey we present the analysis based on a Watson Hamiltonian for an asymmetric one-top rotor of the 13C-substituted ethyl cyanide 13CH3CH2CN, CH313CH2CN and CH3CH213CN in the frequency range 480–650?GHz and 780–990?GHz. Methods. The rotational spectra of the three species were measured with a submillimeter spectrometer (50–990?GHz) using solid-state sources. Results. A new set of spectroscopic parameters was determined from a least-squares fit procedure for each isotopologue. These parameters permit a new accurate prediction of rotational lines suitable for an astrophysical detection in the submillimeter wave range.