THE MILLIMETER-WAVE AND SUBMILLIMETER-WAVE SPECTRUM OF GAUCHE-ETHYL ALCOHOL

We report an investigation of the rotational-torsional spectrum of the gauche rotational isomers of ethyl alcohol in the 51-505 GHz frequenc y region. Over a thousand transitions between rotational levels in the gauche substates of the ground OH torsional state have been measured and assigned. These transitions involve rotational quantum numbers J a nd K-a up to 30 and 15, respectively, and are of two types: a-type tra nsitions between levels in either the gauche+ or the gauche- substate, and c-type transitions between rotational levels in the different sub states, The majority of these transitions have been fit satisfactorily using a two-state Hamiltonian based on the fixed framework axis metho d (FFAM). The rotation, distortion, and interaction constants have bee n determined along with the energy difference between the two gauche s ubstates, The derived constants can be used to predict many more trans itions accurately for astronomical purposes. The J and K-a region wher e the two-state analysis can be used has been determined. The basis fo r a three-state analysis including the trans substate is presented and the applicability of the FFAM approach is discussed. (C) 1996 Academi c Press, Inc.