New measurements of tenK=1 lines, including sixQtype and fourRtype, were made on the completely protonated species of the water dimer. For some of these lines, as well as for someK=0 transitions known from the literature, Stark coefficients were determined, and these Stark coefficients provide a confirmation of the assignments. The newK=1 measurements show that the splitting associated with the (HF)2hyphen;like tunneling motion decreases from about 19.5 GHz forK=0 to about 16.2 GHz forK=1. To understand the fact thatK=1 lines are populated in our 1 K beam, we must assume, in accordance with the results of beam studies on other molecules, that levels of different nuclear spin modification relax separately. In an attempt to gain information on tunneling splittings other than that caused by the (HF)2hyphen;like motion, we have made new measurements on 1ndash;0 and 2ndash;1 transitions withK=0 for several partially deuterated species, in which the (HF)2hyphen;like motion cannot occur. Small splittings ranging from 4 to 145 MHz were observed. Because of the nature of the tunneling motions involved, these new data yield only the difference of the tunneling splitting in the upper and lower states of the transition.
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