Vibrational Spectroscopy of Ethanol Molecules and Complexes Selectively Prepared in the Gas Phase and Adsorbed on Large Argon Clusters

Molecular beam depletion spectroscopy (MBDS) has been employed to study the dissociation of ethanol monomers [C 2 H 5 OH], dimers [(C 2 H 5 OH) 2 ], and trimers [(C 2 H 5 OH) 3 ]. In the spectral region between 870 and 1100 cm -1, which was accessed with a CO 2 laser, four vibrational modes were investigated: the symmetric and asymmetric CCO stretches and the in-plane and out-of-plane rocking modes. Contributions from larger ethanol polymers have been eliminated by dispersing the (C 2 H 5 OH) n clusters with a secondary He beam and measuring the laser-induced depletion off-axis in the scattered cluster beam. To study the C 2 H 5 OH monomer, ethanol molecules were deposited on large Ar N clusters employing the pickup technique. Ethanol dimers and trimers attached to argon clusters have been studied as well. In a computational approach, the structures of ethanol dimers and trimers have been determined by total energy minimization. These theoretical results are of great value for the interpretation of the experimental data as far as the expected splitting of vibrational bands is concerned. The present investigations allow us to give a consistent interpretation of the available data ranging from the gas phase to the liquid as well as to the bulk matrix.