OBSERVATION OF A NEW VIBRATIONAL MODE OF $(D_{2}O)_{2}$ NEAR $68 cm^{-1}$ USING TUNABLE FAR-INFRARED LASER SPECTROSCOPY

Abstract

We have measured the far-infrared vibration-rotation-tunneling (VRT) spectrum of an intermolecular vibration of $(D_{2}O)_{2}$ near $68 cm^{-1}$. In addition, further transitions of the VRT band of $(D_{2}O)_{2}$ previously reported by $Pugliano et al^{1}$ have been observed. By considering symmetry restraints on the selection rules, these bands have been assigned to the out-of-plane H-bond torsional and in-plane acceptor waggins modes predicted by many theoretical $calculations^{2}.$ The experimental-theoretical discrepancy in the measured frequencies of these bands indicates the importance of a fully coupled six-dimmensional calculation of the dynamics for the water dimer.