Mechanisms for free electron production in energy loss by charged particles in gaseous targets

Ions transversing matter primarily lose energy via ionizing collisions. Although detailed information about the energy loss in the collisions can be obtained by studying the emitted electron spectra, no information about the final state of the target is obtained. In order to provide this information, the authors measured the individual cross sections for the various target charge states which occur as a result of direct ionization, electron capture by the projectile, and (in the case of He/sup +/ impact) electron loss by the projectile. These measurements were performed over a broad range of impact energies for H/sup +/, He/sup +/ and He/sup 2+/ impact on rare gases and are currently in progress for H/sup o/ and He/sup o/ impact. Thus a complete picture of energy loss by fast H/sup +/ and He/sup 2+/ ions slowing down in gaseous media is obtained. The authors found that multiple ionization processes are extremely important processes and sometimes are the primary sources of free electrons