Static and dynamic charging of molecular films at interfaces is important in many diverse fields of science and technology. In this report our recent study of the static positive and negative charging of solid layers of water will be discussed. A very stable negative (electrons induced) charging at the water-vacuum interface has been recorded. It functions like a nano-capacitor, accumulating well defined amount of charges and develops electrical fields of more than 106 V/cm, near the discharge threshold. The role of such electrical fields on the photochemistry of trapped molecules within the ice film, as a possible model for e.g. interstellar photo-activity, will be discussed.

Transient charging of nano-scale silicon sharp edges within porous silicon matrix were studied for their effect on photo-reactivity. It was found that laser induced, transient, dynamic charging lead to photo-desorption of atoms (Xe) and molecules (N2O, CO). Photo-induced desorption (PID) cross sections larger by up to 3 orders of magnitude compared to those recorded on flat silicon surfaces were measured. Possible tip-enhanced desorption mechanism and its potential application in photo-catalysis will be discussed.

Finally, the role of reduced, partially charged, oxide surface sites on diffusivity and reactivity of metallic clusters will be discussed as well.