Interaction of NaCl with solid water

The interaction of NaCl with solid water, deposited on tungsten at 80 K, was investigated with metastable impact electron spectroscopy (MIES) and ultraviolet photoelectron spectroscopy (UPS) (He I). We have studied the ionization of Cl(3p) and the 1b1, 3a1, and 1b2 bands of molecular water. The results are supplemented by first-principles density functional theory (DFT) calculations of the electronic structure of solvated Cl− ions. We have prepared NaCl/water interfaces at 80 K, NaCl layers on thin films of solid water, and H2O ad-layers on thin NaCl films; they were annealed between 80 and 300 K. At 80 K, closed layers of NaCl on H2O, and vice versa, are obtained; no interpenetration of the two components H2O and NaCl was observed. However, ionic dissociation of NaCl takes place when H2O and NaCl are in direct contact. Above 115 K solvation of the ionic species Cl− becomes significant. Our results are compatible with a transition of Cl− species from an interface site (Cl in direct contact with the NaCl l...