The Millimeter- and Submillimeter-Wave Spectrum of the Trans and Gauche Conformers of Ethyl Formate

Since methyl formate (HCOOCH₃) is found to have a high abundance in hot molecular cores and other types of clouds in the galactic center, it is reasonable to search among such sources for detectable abundances of the more complex analog ethyl formate (HCOOC₂H₅). Following a previous study of the millimeter-wave spectrum of ethyl formate, we have extended the analysis of the vibrational ground state of the trans and gauche conformers of ethyl formate into the submillimeter-wave range. Over 2200 new spectral lines have been measured and analyzed at frequencies up to 380 GHz. Fitting the data for each conformer to a Watson A-reduced asymmetric-top Hamiltonian has allowed us to predict the frequencies and intensities of many more transitions through 380 GHz.