Interactions of oxalic acid and ice on Cu surface.
The interactions between oxalic acid (C 2H 2O 4) and H 2O on a polycrystalline Cu surface have been investigated by reflection-absorption infrared spectroscopy (RAIRS) and temperature-programmed desorption (TPD) methods. The desorption of H 2O and C 2H 2O 4 was studied; we found that the ice desorption temperature increases with the ice-film thickness. Desorption of the C 2H 2O 4 layer involves a structural modification and sublimation. The H 2O/C 2H 2O 4 and C 2H 2O 4/H 2O interfaces and the codeposited C 2H 2O 4+H 2O were prepared on the Cu surface by varying deposition sequences of gaseous C 2H 2O 4 and H 2O at 155 K. We found that the interaction between ice and C 2H 2O 4 does not lead to the H 2O-induced deprotonation of C 2H 2O 4 in a temperature range 155-283 K. However, H-bonding interactions between H 2O and C 2H 2O 4 can lead to the formation of a metastable oxalic acid-ice complex in the C 2H 2O 4/H 2O and C 2H 2O 4+H 2O systems during the TPD process. Desorption of H 2O from the C 2H 2O 4/H 2O/Cu system is suggested to involve the diffusion of H 2O through the top C 2H 2O 4 layer. H 2O desorption is followed by a rearrangement of C 2H 2O 4 to form a C 2H 2O 4 adlayer on Cu in the C 2H 2O 4+H 2O system. These experimental findings suggest that C 2H 2O 4 is not ionized on snow and ice in the polar boundary layer and at upper tropospheric temperatures ( approximately 240 K).
Yan
Hui
H
Wadsworth Center, New York State Health Department, Albany, New York 12201-0509, USA.
Chu
Liang T
LT
D000327:Adsorption; D002627:Chemistry, Physical / Q000379:methods; D003300:Copper / Q000737:chemistry*; D003460:Crystallization; D004058:Diffusion; D004867:Equipment Design; D007053:Ice; D008962:Models, Theoretical; D015394:Molecular Structure; D019815:Oxalic Acid / Q000737:chemistry*; D011522:Protons; D013499:Surface Properties; D013696:Temperature; D014867:Water / Q000737:chemistry
D007053:Ice; D011522:Protons; D014867:Water; D003300:Copper; D019815:Oxalic Acid