Pseudorotation in the D_2O trimer
Far-infrared spectra of Ar/D_2O 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 (D_2O)_398 cm^(−1) a-type band reported by Liu et al. [J. Am. Chem. Soc. 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 (D_2O)_3 and (H_2O)_3 are presented as a guide to future experimental searches.
© 1994 Elsevier Science B.V. Received 8 July 1994; in final form 23 August 1994. The authors thank Paul Stockman and Elizabeth Olsen for experimental help on numerous occasions as well as helpful discussions, and also the generosity of the Saykally group, particularly J. Loeser, M. Elrod and K. Liu, for sharing their data with us and discussing their findings in detail prior to publication. This work was motivated and aided by the breakthrough accomplished by the Saykally group, and this work would have not been possible without their contributions. Funding for this research was provided by an NSF-PYI award to GAB ( CHE-8957228 ), and by the generous support of the David and Lucille Packard and Alfred P. Sloan Foundations. Division of Geological and Planetary Sciences, California Institute of Technology, Contribution No. 5427.