PNNL

Abstract

[1] on our Letter ‘‘Dissociation of Water Buried under Ice on Pt(111)’’ [2] raises some interesting points. In the original Letter, we made two sets of observations: (1) that thick water films ( > 150 monolayers) absorbed at temperatures higher than usually used in ultrahigh vacuum studies ( > 153 K for H2O) on Pt(111) showed a positive charging that behaved much as would be expected for positive ions trapped on the ice surface during the film growth, and (2) that the thick ice films, when desorbed carefully in a two-step process, showed a consistent pattern of high temperature programmed desorption (TPD) features spanning 170 to 200 K. Based on this, we concluded that water was dissociating at the Pt(111) surface under the thick ice film and in amounts greater than a few tenths of a monolayer. Zimbitas et al. [1] argue that the high temperature peaks can be explained by a nonwetting phenomena that they see for adsorption above 152 K (for H2O), that leads to large water clusters sitting upon a single monolayer of water. Thus, they conclude that our evidence for dissociation of water is weak.