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HUI LI, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada; A. R. W. MCKELLAR, Steacie Institute for Molecular Sciences, National Research Council of Canada, Ottawa, Ontario K1A OR6, Canada; ROBERT J. LE ROY AND PIERRE-NICHOLAS ROY, Department of Chemistry, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada.
The infrared spectra of several isotopologues of the CO2-( para -H2)2 trimer have been predicted by applying exact basis-set calculations to a global potential energy surface which is defined as a sum of the accurately known two-body para -H2--CO2 and para -H2-- para -H2 potentials.\footnote H. Li, P.-N. Roy and R.J. Le Roy, J. Chem. Phys. (2010, submitted);~ K. Patkowski, W. Cencek, P. Jankowski, K. Szalewicz, J.B. Mehl, G. Garberoglio and A.H. Harvey, J. Chem. Phys. 129, 094304 (2010). These results are compared with new spectroscopic measurements, for which sixteen transitions have been assigned. A reduced-dimension treatment of the para -H2 rotation has been employed by performing an exact hindered-rotor average.~ Three-body effects and the quality of the potential are discussed. We present a new technique for representing the three-dimensional para -H2 density in the body-fixed frame. It shown the two para -H2 molecules are localized much more closely together than is the case for the two He atoms in the analogous CO2--(He)2 system.