Asymmetric transport efficiencies of positive and negative ion defects in amorphous ice.

: Hydronium (H(3)O(+)) ions at an ice surface penetrate into its interior over a substantially longer distance than hydroxide (OH(-)) ions. The observation was made by conducting reactive ion scattering and infrared spectroscopic measurements for the acid-base reaction between surface H(3)O(+) (or OH(-)) and NH(3) (or NH(4)(+)) trapped inside an amorphous ice film at low temperature (<100 K). The study reveals very different transport efficiencies of positive and negative ion defects in ice. This difference is explained by the occurrence of an efficient proton-relay channel for H(3)O(+), which does not exist for OH(-).