FAR-IR LASER VIBRATION-ROTATION-TUNNELING SPECTROSCOPY OF WATER CLUSTERS

$^{1.}$ N. Pugliano, J. Cruzan, and R. J. Saykally, J. Chem. Phys., (1993), in press. $^{2.}$N. Pugliano, and R. J. Saykally, Science 257, 1937-1940(1993).Author Institution: Department of Chemistry, University of California; Department of Chemistry, University of PennsylvaniaRecent tunable far-infrared laser spectroscopic studies of water clusters have been carried out as a continuation of our approach to investigating intermolecular forces and internal tunneling dynamics of chemically and biologically important systems. Following the first report of FIR VRT transitions of $(D_{2}O)_{2}$ and $(D_{2}O)_{3}$ by Pugliano $et al.,^{1.2}$ we have measured new intermolecular rovibrational bands for $(H_{2}O)_{2}. (D_{2}O)_{2}$. and $(D_{2}O)_{3}$. Preliminary analysis shows that the first observed band for $(H_{2}O)_{2}$ arises from $K_{a}=0 \leftarrow 1$ transitions around $103 cm^{-1}$, the three newly observed VRT $K_{a}=0 \leftarrow 0$ subbands for $(D_{2}O)_{2}$ around $103 cm^{-1}$ correspond to a second intermolecular vibrational mode. A second vibrational mode of $(D_{2}O)^{3}$ has also been observed at $96 cm^{-1}$