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

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 hands 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.