15min:
THEORETICAL AND EXPERIMENTAL STUDY OF THE ROVIBRATIONAL SPECTRA OF CO2-( para -H2)-He TRIMERS.

HUI LI, Institute of Theoretical Chemistry, State Key Lab. of Theoretical & Computational Chemistry, Jilin Univ., 2519 Jiefang Rd, Changchun 130023, P.R.China; Chemistry Dept., Univ. of Waterloo, Waterloo, Ontario N2L 3G1, Canada; ROBERT J. LE ROY, PIERRE-NICHOLAS ROY, Chemistry Dept., Univ. of Waterloo, Waterloo, Ontario N2L 3G1, Canada; A. R. W. MCKELLAR, Steacie Institute for Molecular Sciences, NRCC, Ottawa, Ontario K1A OR6, Canada.

Clusters of p -H2 had been predicted to exhibit superfluid behavior twenty years ago, but direct observation of this phenomenon was elusive until our recent work combining experimental measurments and theoretical simulations of the non-classical rotational inertia and superfluid response of p -H2 clusters doped with CO2. However, the size-dependent superfluid response of those clusters reached a maxmum at N\!=\!12, and the clusters become frozen at larger N. It is therefore interesting to examine the effect of adding helium atoms to a pure p -H2 shell around a CO2 chromophore, and to investigate their effect on the superfluid response of CO2-( p -H2)N for N\!>\!12. This will help us understand the role of helium as a `second solvent' species, and help explain experiments that had been presented as evidence of superfluidity of doped hydrogen clusters embedded in helium nanodroplets. Exact quantum calculation of infrared and microwave spectra for dopant molecules attached to two pure He atoms or two pure p -H2 molecules, respectively, have been reported by Wang and co-workers and by Li et al .\footnote X.-G. Wang, T. Carrington Jr., J. Tang and A.R.W. McKellar, Can. J. Phys. 87, 417 (2009); J. Phys. Chem. A 113, 13331 (2009); Can. J. Phys. 88, 779 (2010); H. Li, P.-N. Roy and R.J. Le Roy, J. Phys. Chem. (2011, submitted ).~ To date, however, no such calculations have been reported for mixed p -H2/He solvent species. The present paper therefore extends such work to the case of one p -H2 and one He atom attached to one CO2 dopant molecule. Three-dimensional p -H2 and helium densities in the body-fixed frame are presented, and compared with those for the analogous CO2--(He)2 and CO2--( p -H2)2 trimers.