THE SUBMILLIMETER ROTATION TUNNELING SPECTRUM OF (D2O)2

By direct absorption of submillimeter radiation in a planar supersonic jet, we have measured Ka=1→Ka=2 transitions of the fully deuterated water dimer (D2O)2 in the region between 350 and 430 GHz. Several previously unknown constants have been derived. The A-rotational constant is determined as 120327.492(32) MHz. The sum or the difference of the largest tunneling splittings for Ka=1 and Ka=2 is approximately 21 GHz. The tunneling matrix element h2v has been found to be a factor of 100 smaller than in (H2O)2. © 1990.