Multiple Ionisation and High Charge Effects in Electron Spectra from Impact of 9 MeV/u Ions on Carbon

Abstract

We measured energy spectra of electrons emitted from sputter-cleaned amorphous carbon targets bombarded with swift ions of constant velocity (9 MeV/u, vP = 19v0) with a new UHV set-up at the heavy ion accelerator GANIL. The charge of the projectile qp varied from 6 to 45. At large electron energy, a qp2 scaling law is observed. For energies below the 1s ionisation threshold, strong reduction effects with increasing qp occur. A carbon Auger hypersatellite line due to double ionisation of the K shell appears for high projectile charge only. From these Auger spectra, the ratio of double and single ionisation was deduced as a function of qp and found to increase from a threshold up to a saturation.