Extension of panoramic cluster jet spectroscopy into the far infrared: Low frequency modes of methanol and water clusters

Abstract

The ragout-jet FTIR spectroscopy of hydrogen-bonded clusters is extended into the far infrared range, where intermolecular librational and translational modes occur. For large H₂O, D₂O, and CH₃OD clusters, the resulting absorption bands are detected and compared to gas phase and condensed phase data. The potential for cluster-size resolved spectra is explored in the case of the OD bending mode of CH₃OD. The integrated band strength ratio between the CO stretching and the OD bending mode is found to increase by a factor of four upon clustering. The strong OH torsion band of the free monomer is transformed quantitatively into high frequency librations upon clustering in the jet. For H₂O and D₂O clusters, both librational and translational modes are detected, in good agreement with available condensed phase data. The cluster distribution is characterized by comparing to OD stretching spectra under identical conditions.