Surface chemical properties of eutectic and frozen NaCl solutions probed by XPS and NEXAFS.
We study the surface of sodium chloride-water mixtures above, at, and below the eutectic temperature using X-ray photoelectron spectroscopy (XPS) and electron-yield near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. The NaCl frozen solutions are mimicking sea-salt deposits in ice or snow. Sea-salt particles emitted from the oceans are a major contributor to the global aerosol burden and can act as a catalyst for heterogeneous chemistry or as cloud condensation nuclei. The nature of halogen ions at ice surfaces and their influence on surface melting of ice are of significant current interest. We found that the surface of the frozen solution, depending on the temperature, consists of ice and different NaCl phases, that is, NaCl, NaCl·2H(2)O, and surface-adsorbed water.
Laboratory for Radio- and Environmental Chemistry, Paul Scherrer Institut, 5232 Villigen, Switzerland.
Adéla
A
Křepelová
Thomas
T
Huthwelker
Hendrik
H
Bluhm
Markus
M
Ammann