CARBONIC-ACID BY ION-IMPLANTATION IN WATER CARBON DIOXIDE ICE MIXTURES/

We present the results of experiments performed by keV ion (He and H) bombardment of frozen mixtures of H2O:CO2 and of pure CO2 ice. Using k eV He ions we confirm the already reported measurement of carbonic aci d (H2CO3) production in an ice mixture of frozen water and carbon diox ide (1:1) after irradiation by 0.7 MeV H ions (Moore, M. H., and R. K. Khanna 1991. Spectrochim. Acta 47, 255-262; Moore, M. H., R. K. Khann a, and B. Donn 1991. J. Geophys. Res. E 96(2), 17,541-17,545.). Contra ry to a previous report (Pirronello, V., W. L. Brown, L. J. Lanzerotti , K. J. Marcantonio, and E. H. Simmons 1982. Astrophys. J. 262, 636-64 0.), formaldehyde (H2CO), if any, is not a major product. Implantation with hydrogen ions demonstrates that carbonic acid is formed even if the irradiated target is pure CO2; i.e., the implanted ion is incorpor ated into the target and forms new bonds. Some possible astrophysical applications on Solar System objects or (pre-solar) interstellar grain s are discussed. (C) 1997 Academic Press