Spectrum of ^18^O-methyl formate (HCO^18^OCH_3_)

Very accurate spectroscopic constants are obtained in a comprehensive laboratory analysis of rotational spectra. These constants can be used to predict with very high precision the frequencies of transitions that have not been measured in the laboratory.

In this work, an experimental study and its theoretical analysis is presented for two ^18^O-methyl formate isotopologues in order to detect for the first time both isotopologues in Orion KL. The experimental spectra of both isotopologues of methyl formate have been recorded in the microwave and sub-mm energy range from 1 to 660GHz. Both spectra have been analysed by using the Rho-Axis Method (RAM) which takes into account the CH3 internal rotation.