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Covalent and Ionic States of Strong Acids at the Ice Surface
Author(s) -
Devlin J. Paul,
Uras Nevin,
Rahman Mohammed,
Buch Victoria
Publication year - 1999
Publication title -
israel journal of chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.908
H-Index - 54
eISSN - 1869-5868
pISSN - 0021-2148
DOI - 10.1002/ijch.199900033
Subject(s) - chemistry , adsorption , ionic bonding , chemical physics , polar , ion , organic chemistry , physics , astronomy
The relationship between the degree of ionization and the environment of a strong acid is of basic scientific interest. Often this relationship reduces to the interdependence of ion/acid hydration and proton transfer. Despite the presence of pure water, the surface of crystalline ice, particularly at cryogenic temperatures, is one of limited (controlled?) availability of water of hydration. Here, the detailed nature of the ice surface and the states of strong acids adsorbed to ice at cryogenic temperatures are examined. These subjects are of special current interest since the ability to model the complex chemistry that occurs on the surfaces of water‐rich particles in the atmosphere, particularly in the stratosphere over the polar regions, requires a valid concept of the acid‐ice interface. Our combined spectroscopic and simulation studies have identified the surface of free‐standing ice particles as badly disordered, with a range of water‐ring sizes and an increased level of H‐bond saturation relative to an ordered ice surface. FT‐IR results are reported for the interaction of the surface of such ice particles with submonolayer amounts of adsorbed DCl, DBr, and HNO 3 and for multilayer exposure to DCl. The DCl and DBr adsorbed states demonstrate behavior familiar from observations on strongly bound molecular adsorbates. Two methods have been devised for exposure of the nanocrystals to HNO 3 One gives an ionic state initially, while the initial state of the other approach is molecular. In both instances, the system is observed to evolve, with time/warming, towards a common mixed molecular–ionic adsorbed state.