keV-energy ion and atom bombardment of low-temperature solids: radiation damage, sputtering, and mechanism

Experimental evidence available for the phenomena induced by the low energy bombardment of frozen gases with keV energy ions and atoms is summarized. The results can be understood qualitatively in terms of a model incorporating (i) sputtering and primary damage center formation in the collision cascade regime, (ii) conversion of primary to secondary damage centers in the elastic collision spike which develops subsequently, accompanied by flow of a portion of the hot gas from the spike region into vacuum and the freezing of the remainder on the crater walls, and (iii) selective evaporation of the least firmly held components of the solvation shells surrounding those ejected secondary damage centers which are charged. New results are reported for keV-energy sputtering yields of the solid rare gases and for spectroscopically observed radiation damage in several other frozen gases. They are compatible with the model. (author)