IONIZING COLLISIONS OF ELECTRONS WITH H2O MOLECULES IN ICE AND IN WATER

Total inelastic cross sections for electron impact on H2O molecules in condensed matter phases have been calculated for incident energies fr om ionisation thresholds up to about 3000 eV. They approach total ioni sation cross sections in the high energy limit. The cross sections are calculated through an absorption potential for which a model charge d ensity is developed for H2O in ice. For H2O in liquid phase we use the charge density of the free molecule. Differences in the properties of H2O in condensed phases give rise to differences in the respective cr oss sections. H2O (ice) exhibits the highest inelastic cross sections, with H2O (liq) showing the lowest values from among the three phases, in the peak region. Our cross sections for H2O (liq) are higher than the previous calculations, based on the Born approximation along with model generalised oscillator strength. (Int J Mass Spectrom 177 (1998) 137-141) (C) 1998 Elsevier Science B.V.