Publication Date:
2014-12-30
Description:
Publication date: April 2015 Source: Icarus, Volume 250 Author(s): C. Mejía , A.L.F. de Barros , E. Seperuelo Duarte , E.F. da Silveira , E. Dartois , A. Domaracka , H. Rothard , P. Boduch Porous water ice and water ice mixtures H 2 O:X (X = CO, CO 2 and CH 4 ) produced at 15 K, with film thicknesses in the 0.5–1 μm range, were irradiated by swift ions and monitored by mid-infrared spectroscopy (FTIR). The analysis of the evolution of the pure water ice infrared absorption on ion beam dose reveals a strong correlation among three quantities: (i) the absorbance of the most intense band (3250 cm −1 ), (ii) the wavelength of the maximum absorbance of this band and (iii) the absorbance of the OH-dangling bonds. This correlation is interpreted as indications of the water ice compaction by irradiation: as the beam fluence increases, the ice porosity decreases, the dangling bond peaks collapse and the area and position of the 3250 cm −1 band vary exponentially, all of them evolving with the same compaction cross section ( σ c ). The linear dependence σ c ∝ S e ( S e being the electronic stopping power) is observed for both pure and mixed water ices, confirming previous results. We suggests that the infrared absorption A -value varies with dose as ( 1 - ζ e - D / D 0 ) during the compaction process ( D 0 = 0.2 eV/molec being the effective energy density to eliminate the OH-db, and ζ is a parameter characterizing the porosity). These findings may be used as a diagnostic tool to probe the morphology of water ices occurring in the outer Solar System and in the ISM.
Print ISSN:
0019-1035
Electronic ISSN:
1090-2643
Topics:
Physics
