title: Emergence of Solvent-Separated Na+-Cl-Ion Pair in Salt Water: Photoelectron Spectroscopy and Theoretical Calculations.
abstract: Solvation of salts in water is a fundamental physical chemical process, but the underlying mechanism remains unclear. We investigated the contact ion pair (CIP) to solvent-separated ion pair (SSIP) transition in NaCl(H2O)nclusters with anion photoelectron spectroscopy and ab initio calculations. It is found that the SSIP type of structures show up at n = 2 for NaCl-(H2O)nanions. For neutral NaCl(H2O)n, the CIP structures are dominant at n < 9. At n = 9-12, the CIP structures and SSIP structures of NaCl(H2O)nare nearly degenerate in energy, coincident to the H2O:NaCl molar ratio of NaCl saturated solution and implying that the CIP and SSIP structures can coexist in concentrated solutions. These results are useful for understanding the solvation of salts at the molecular level.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Gao-Lei
authors.initials: GL
authors.lastname: Hou
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
authors.forename: Cheng-Wen
authors.initials: CW
authors.lastname: Liu
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.
authors.forename: Ren-Zhong
authors.initials: RZ
authors.lastname: Li
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Hong-Guang
authors.initials: HG
authors.lastname: Xu
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Theoretical and Computational Chemistry, College of Chemistry and Molecular Engineering, Peking University , Beijing 100871, China.
authors.forename: Yi Qin
authors.initials: YQ
authors.lastname: Gao
authors.affiliation: Beijing National Laboratory for Molecular Sciences, State Key Laboratory of Molecular Reaction Dynamics, Institute of Chemistry, Chinese Academy of Sciences , Beijing 100190, China.|University of Chinese Academy of Sciences , Beijing 100049, China.
authors.forename: Wei-Jun
authors.identifier: http://orcid.org/0000-0002-9136-2693
authors.initials: WJ
authors.lastname: Zheng