TITLE

Mechanistic study of proton transfer and H/D exchange in ice films at low temperatures (100–140 K)

AUTHOR(S)
Chang-Woo Lee; Poong-Ryul Lee; Young-Kwang Kim; Heon Kang
PUB. DATE
August 2007
SOURCE
Journal of Chemical Physics;8/28/2007, Vol. 127 Issue 8, p084701
SOURCE TYPE
Academic Journal
DOC. TYPE
Article
ABSTRACT
We have examined the elementary molecular processes responsible for proton transfer and H/D exchange in thin ice films for the temperature range of 100–140 K. The ice films are made to have a structure of a bottom D2O layer and an upper H2O layer, with excess protons generated from HCl ionization trapped at the D2O/H2O interface. The transport behavior of excess protons from the interfacial layer to the ice film surface and the progress of the H/D exchange reaction in water molecules are examined with the techniques of low energy sputtering and Cs+ reactive ion scattering. Three major processes are identified: the proton hopping relay, the hop-and-turn process, and molecular diffusion. The proton hopping relay can occur even at low temperatures (<120 K), and it transports a specific portion of embedded protons to the surface. The hop-and-turn mechanism, which involves the coupling of proton hopping and molecule reorientation, increases the proton transfer rate and causes the H/D exchange of water molecules. The hop-and-turn mechanism is activated at temperatures above 125 K in the surface region. Diffusional mixing of H2O and D2O molecules additionally contributes to the H/D exchange reaction at temperatures above 130 K. The hop-and-turn and molecular diffusion processes are activated at higher temperatures in the deeper region of ice films. The relative speeds of these processes are in the following order: hopping relay>hop and turn>molecule diffusion.
ACCESSION #
26469918

 

Related Articles

Share

Read the Article

Courtesy of THE LIBRARY OF VIRGINIA

Sorry, but this item is not currently available from your library.

Try another library?
Sign out of this library

Other Topics