title: Insights into gas-phase structural conformers of hydrated rubidium and cesium cations, M(+)(H2O)(n)Ar (M = Rb, Cs; n = 3-5), using infrared photodissociation spectroscopy.
abstract: Infrared photodissociation (IRPD) spectra of M(+)(H2O)nAr (M = Rb, Cs; n = 3-5) with simultaneous monitoring of [Ar] and [Ar+H2O] fragmentation channels are reported. The comparison between the spectral features in the two channels and corresponding energy analysis provide spectral assignments of the stable structural conformers and insight into the competition between ion-water electrostatic and water-water hydrogen bonding interactions. Results show that as the level of hydration increases, the water-water interaction exhibits the tendency to dominate over the ion-water interaction. Cyclic water tetramer and water pentamer substructures appear in Cs(+)(H2O)4Ar and Cs(+)(H2O)5Ar systems, respectively. However, cyclic water tetramer and pentamer structures were not observed for Rb(+)(H2O)4Ar and Rb(+)(H2O)5Ar systems, respectively, due to the stronger influence of the rubidium ion-water electrostatic interaction. The energy analysis, including the available internal energy and the IR photon energy, helped provide an experimental estimate of water binding energies.
authors: Department of Chemistry, University of Illinois at Urbana-Champaign , Urbana, Illinois 61801, United States.
authors: Haochen
authors: H
authors: Ke
authors: Christian
authors: C
authors: van der Linde
authors: James M
authors: JM
authors: Lisy
mesh_terms: D002414:Cations, Monovalent; D002586:Cesium / Q000737:chemistry*; D005740:Gases / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D012413:Rubidium / Q000737:chemistry*; D013055:Spectrophotometry, Infrared / Q000379:methods; D055672:Static Electricity; D013816:Thermodynamics; D014867:Water / Q000737:chemistry*
chemical_list: D002414:Cations, Monovalent; D005740:Gases; D014867:Water; D002586:Cesium; D012413:Rubidium