Alpha-Recoil and Fission Fragment Induced Desorption of Secondary Ions

Abstract

The energy loss of 100 keV particles in matter is dominated by nuclear stopping power. One would expect that mass and energy spectra of secondary particles, released from a solid surface under the bombardment with projectiles of these energies should reflect both kinds of energy losses. In the following, radioactive decay processes are used to produce the high energetic projectiles: the α-active isotope Am-241 emitting the 92 keV-revoil nucleus Np-237 and the spontaneous fission isotope Cf-252 emitting fragments with masses around 100 and energies of 80–120 Mev. Mass and energy spectra are obtained by a time-of-flight technique [1], where the accompanying nuclear radiation produces the start signal. The mass spectra were taken from Am evaporated onto a carbon foil. In this work only the ions C⁺, CH⁺, CH₂ ⁺and CH₃ ⁺ are investigated, which are released from the carbon matrix or from contamination layers. Generally, secondary ion desorption induced by α-recoil particles shows more fragmentation than fission fragment induced desorption.

Work supported by the Deutsche Forschungsgemeinschaft.