SECONDARY-ION EMISSION FROM FROZEN ARGON BY CF-252 FISSION FRAGMENTS

In order to study sputtering of Van-der-Waals solids by MeV ion impact , films of solid argon condensed onto a metallic substrate at a temper ature of 10 K were irradiated by Cf-252 fission fragments. The seconda ry ions emitted from the surface were investigated by a time-of-flight technique. The mass spectra are dominated by a cluster series Ar-n(+) with n ranging from 1 to about 30. Comparatively high absolute ion yi elds were determined; the yield of Ar+ was 48 ions/impact. The mass li ne of Ar+ was broadened due to ejection energies of up to 50 eV. The l ine shape of the cluster ions indicates delayed particle emission. Som e of the observed phenomena are not typical for electronic sputtering at MeV energies; they are briefly discussed. These are the first and p reliminary results of a systematic exploration of high energy sputteri ng from solid rare gases.