Electron-capture and impact-ionisation cross sections of Nq+in atomic hydrogen

Cross sections for electron capture by N q+ (1<or=q<or=5) incident on atomic hydrogen have been measured in the velocity range (0.3-5.2)*10 8 cm s -1 . A classical trajectory Monte-Carlo method was used to calculate the electron-capture and impact-ionisation cross sections for incident-ion charge state 3<or=q<or=7. The experimental and theoretical electron-capture cross sections are in good agreement and are found to scale as q eff 2 , where q eff may be obtained from spectroscopic energy levels. The impact-ionisation cross sections rise to a maximum around v=4-6*10 8 cm s -1 , above which impact ionisation dominates electron capture as the principal H electron-loss process.