SUM-FREQUENCY GENERATION INVESTIGATION OF WATER AT THE SURFACE OF H2OH2SO4 AND H2O/CS2SO4 BINARY-SYSTEMS/

The vibrational structure of water at the air/solution interface of an ionic solution has been obtained for the first time. Using vibrationa l sum frequency generation it is determined that ions in solution have a large orientational effect on the structure of the surface water. E lectrolytic solutions, ionic in nature, cause water to be oriented int o a more regular hydrogen-bonded network through an electric double la yer at the interface. In electrolytic solutions where molecular or ass ociated H2SO4 or Cs2SO4 species dominate, the surface water molecules are bound into hydrate complexes. These effects are explained using ha rd soft acid base (HSAB) theory. (C) 1998 Elsevier Science B.V. All ri ghts reserved.