A Simple Model for Ice Compaction Data Induced by Low Energy Ion Irradiation

A connection between the compaction of amorphous solid water (ASW) during energetic ion irradiation and the disappearing of water dangling bonds (OH-db) has been analyzed particularly by the Palumbo et al. and by Baragiola et al. In this work, a further discussion of the process for inducing the compaction is presented. Simple models for OH-db evolution for irradiated water ice are discussed. Literature results on the OH-db disappearance in ices bombarded by 100–200 keV H⁺ ions and on the comparison of porosity and OH-db results for 200 keV Ar⁺ ions are revisited. It is observed that for both, porosity decrease (compaction) and OH-db absorption signal decrease, experimental data can be well fitted by the sum of two decreasing exponentials with similar sets of parameters. Although a clear explanation for this correlation cannot be extracted, it suggests strongly that compaction and OH-db destruction are both triggered by two different processes.