%0 Journal Article
%@ 1089-5639
%A Myshakin, EM
%A Diri, K
%A Jordan, KD
%D 2004
%F pittir:18067
%J Journal of Physical Chemistry A
%N 32
%P 6758 - 6762
%T Theoretical investigation of the neutral precursor of (H <inf>2</inf>O) <inf>6</inf><sup>-</sup>
%U http://d-scholarship-dev.library.pitt.edu/18067/
%V 108
%X In a recent ingenious experiment Diken et al. (Diken, E. G.; Robertson, W. H.; Johnson, M. A. J. Phys. Chem. A 2004, 108, 64) obtained the vibrational spectrum in the OH stretch region of the neutral (H 2O) 6 precursor to the (H 2O) 6 ion. Comparison of the measured spectrum with the calculated harmonic vibrational spectra of various low-energy isomers of (H 2O) 6 led these authors to conclude that the observed spectrum is due to the book isomer, although agreement between theory and experiment is only qualitative. In the present study a hybrid MP2/QCISD method is used to overcome a shortcoming of earlier theoretical calculations of the harmonic spectra of low-energy (H 2O) 6 isomers, and the coupling of the fundamentals with overtones and combination states is accounted for by means of a cubic force-field approximation. The results of these calculations provide further support for the assignment of the book form of (H 2O) 6 as the precursor of the dominant observed (H 2O) 6- isomer.