Abstract
Deuteron magnetic resonance study of RbD3(SeO3)2 was made between −165 and 14°C. Electric quadrupole coupling constants and directions of the principal axes of EFG tensors were obtained in the paraelectric phase. There are three types of hydrogen bonds with different behavior which play some roles at phase transition. The relation between the temperature dependence of the resonance spectra and that of doubly degenerate soft-mode is discussed.