Abstract.  Energy deposition by particle beams interacting with gas targets leads to the formation of a light emitting plasma. Energy transfer from the beam to the target increases with increasing charge and decreasing velocity of the projectile, according to the Bethe – Bloch formula. In the case of heavy ion beams interacting with dense gas targets both the primary projectiles and the secondary electrons contribute to the formation of the plasma. Two extreme cases of particle beam induced plasmas and their light emitting processes will be described: Plasmas induced by high energy heavy ion beams and those induced by low energy electron beams. It will be shown that both cases have the potential for producing a high energy density in matter based on the charge- and velocity dependence of the energy deposition described above.

Experiments to study heavy ion beam induced light emission were performed at the synchrotron SIS at the Helmholtzzentrum for heavy ion research, GSI Darmstadt and the Munich Tandem van de Graaff accelerator, Germany.

Experiments using low energy (12 keV) electron beam excitation became possible by using extremely thin (300 nm) silicon nitride entrance foils for the gas target. Noble gases and mixtures of noble gases with molecular gases are used as the target material in most of the experiments which will be described. Population of the excited levels via direct excitation, recombination and gas kinetic processes contribute to the light emitting processes. It will be shown that the formation of so called excimer molecules plays an important role in the gas kinetic processes of dense, particle beam excited rare gases. Their radiative decay can be used to build highly efficient light sources in the vacuum ultraviolet spectral range. Energy transfer processes from the rare gases to other target species can be used to design light sources with a wide variety of emission characteristics.

Spectroscopic studies of electron and ion beam induced fluorescence in the context of particle astro-physics will be presented as an application of particle beam induced light emission for fundamental research. Finally it will be shown that an appropriate choice of target material and beam parameters also allows to realize coherent light sources in the form of ion- or electron beam pumped lasers.

Acknowledgement :
This work has been supported by the German Ministry of Education an Research BMBF, under contract No. 13N9528, the Plasma Physics Group at GSI Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany, and the Maier-Leibnitz Laboratory MLL, Garching, Germany, EU.