MICROWAVE SPECTRUM OF THE D2O DIMER

$^{1}$ J. A. Odutola, T. A. Hu, D. Prinslow, S. E. O'dell, and T. R. Dyke, J. Chem. Phys. 88, 5352 (1988). 2L. H. Coudert, F. J. Lovas, R. D. Suenram, and J. T. Hougen, J. Chem. Phys. 87, 6290 (1987).Author Institution: Molecular Spectroscopy Division, National Institute of Standards and TechnologyExtensive microwave measurements have been made on the (D2O)2 using a pulsed-nozzle Fourier-transform microwave spectrometer and a recently developed electric-resonance Optothermal spectrometer (EROS). The new measurements build on the previous spectroscopic work of Odutola $et al.^{1}$ and Coudert $et al.^{2}$ for the $K=0 A_{1}{^{\pm}}, B_{1}{^{\pm}}$, and $E^{\pm}$ states. Spectra have been recorded between 9 - 110 GHz and include the first observation of the $A_{2}{^{\pm}}$ and $B_{2}{^{\pm}}$ states. The tunneling splitting for the $K=0 A_{2}{^{\pm}}/B_{2}{^{\pm}}$ states is determined to be 1083.303(21) MHz, which is slightly lower than the 1172.115(14) MHz value found previously for the $A_{1}{^{\pm}}/B_{1}{^{\pm}}$ states. In addition, we report the first $K=1$ measurements on $(D_{2}O)_{2}$, giving a tunneling splittings of 1076.616(14) and 992.368(90) MHz for the $A_{1}{^{\pm}}/B_{1}{^{\pm}}$ and $A_{2}{^{\pm}}/B_{2}{^{\pm}}$ states, respectively. Searches have also been made for b or c-type $K=1-0$ transitions predicted near 100 GHz. A number of transitions have been observed but are presently unassigned