Electron impact excitation and ionization of N 4+

An experimental investigation of the electron impact excitation and ionization cross sections of N ⁴⁺ is described. A Van de Graaff accelerator coupled with a gas stripper is used to produce a beam of 2.7 MeV N ⁴⁺ ions which are separated from other charge states by magnetic and electrostatic analysis. The ions are crossed with a variable energy electron beam in a well-defined geometry. Radiation from the excited ions is observed with a photomultiplier downstream from the interaction region. The ions promoted to higher charge states are separated from the primary beam electrostatically and detected with an electron multiplier tube. Chopping of both ion and electron beams is employed. Results are presented for the N ⁴⁺ transition (2s→2p in the collision energy range 125-400 eV.