PSEUDOROTATION IN THE D2O TRIMER

Far-infrared spectra of Ar/D2O supersonic expansions have been recorded between 39 and 44 cm(-1), in which a c-type band centered at 41.1 cm(-1) was observed. This new band, attributed to the cyclic water trimer, has the same ground state rotational constants as the (D2O)(3) 98 cm(-1) a-type band reported by Liu et al. [J. Am. Chem. Sec. 116 (1994) 3507]. Fits of the observed far-infrared band positions to an effective one-dimensional potential require a substantially larger pseudorotation barrier or effective moment of inertia than predicted theoretically. Estimated frequencies of unobserved transitions in the pseudorotation manifolds of (D2O)(3) and (H2O)(3) are presented as a guide to future experimental searches.