Knowledge Bank

As reported last year, molecular beam electric resonance spectroscopy has been used to observe radio frequency and microwave transitions in water dimer produced in supersonic nozzle beam sources. Both $(H2O)2$ and $(D2O)2$ have been studied. Sufficient data have been obtained to provide the following structural parameters: the oxygen-oxygen internuclear distance is 2.98 $\pm$ 0.04 {\AA}, the hydrogen bond is linear to within $10\circ$, and the hydrogen accepting molecule is oriented $50\circ \pm 10\circ$ from the hydrogen bond axis. Very large amplitude vibrations are clearly evident, but all data is consistent with an equilibrium structure having a plane of symmetry.The A component of the electric dipole moment has been measured for two vibrational states in the J = 2, K = 2 and J – 3, K = 3 states yielding$u22=2,5896(7)D,u33=2.5658(11)D$ and $\mu 22=2.6350(11)$ D, and $\mu 33=2.6238(8)$ D.