Ion formation by impact of fast dust particles and comparison with related techniques

Abstract

Fast dissipation of energy on solid surfaces either by particle impact or by pulsed laser irradiation causes similar ionization effects. The excitation functions for ion formation are studied and compared for various excitation radii and energy dissipation fluxes. The goal is to try to understand quantitatively the formation of ions upon impact of cometary dust particles on metal targets, as being used for various in situ investigations on space flight missions. The high impact speeds occurring during these missions cannot be achieved in the laboratory. Therefore also the results of other related techniques are used such as: nanosecond giant laser pulses, secondary ion mass spectrometry, heavy ion induced desorption. The results must be interpreted in terms of the properties of elementary excitation of the solid caused by the primary interactions and their subsequent evolution. A far-from-equilibrium phase transition description is adopted for desorption phenomena, as the quasiequilibrium equation-of-state models had been shown not to be able to describe the mass spectra in this regime. Semiempirical and semi-quantitative simulation and comparison rules for ion formation are discussed and the limiting conditions of validity of the various ion formation models are given.