title: Solvation structure of I- and Na+ on the surface of NaI aqueous solution studied by photodetachment spectroscopy in combination with mass spectrometry.
abstract: We investigated solvation structures of I(-) and Na(+) on an aqueous solution surface by photodetachment spectroscopy and mass spectrometry. An aqueous solution of NaI was introduced into the vacuum as a continuous liquid flow (liquid beam), and the liquid beam was irradiated with a UV laser pulse. The abundance of electrons emitted by the laser excitation was measured as a function of wavelength (photodetachment spectroscopy). For a concentrated aqueous solution of NaI, we observe an absorption peak at longer wavelengths than the charge-transfer-to-solvent band of I(-) in solution. This feature is assigned to the photoabsorption of I(-) at the surface. This finding indicates that when the concentration of NaI is high (>1.0 M), I(-) exists on the solution surface. The identity of the ion clusters ejected from the liquid beam following selective laser excitation of I(-) on the surface or I(-) inside the solution was revealed by mass spectrometry. The mass spectra show that Na rich clusters are formed when I(-) inside the solution is excited, whereas Na rich clusters are hardly formed by the excitation of surface I(-). These findings lead us to conclude that Na(+) does not exist on the surface of the NaI aqueous solution.
authors.affiliation: Department of Basic Science, Graduate School of Arts and Sciences, The University of Tokyo, Komaba, Meguro-ku, Tokyo 153-8902, Japan.
authors.forename: Makoto
authors.initials: M
authors.lastname: Shoji
authors.forename: Keisuke
authors.initials: K
authors.lastname: Kaniwa
authors.forename: Yojiro
authors.initials: Y
authors.lastname: Hiranuma
authors.forename: Olivia
authors.initials: O
authors.lastname: Maselli
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Mafuné
mesh_terms: D007455:Iodine / Q000737:chemistry; D007477:Ions / Q000737:chemistry; D013058:Mass Spectrometry; D015394:Molecular Structure; D012964:Sodium / Q000737:chemistry; D012974:Sodium Iodide / Q000737:chemistry*; D012996:Solutions; D012997:Solvents; D013057:Spectrum Analysis
chemical_list: D007477:Ions; D012996:Solutions; D012997:Solvents; D007455:Iodine; D012964:Sodium; D012974:Sodium Iodide