Electron-capture and impact-ionisation cross sections for partially stripped iron ions colliding with atomic and molecular hydrogen

Cross sections for single-electron capture and for impact ionisation of Fe q+ (q=10,15,20,25) ions incident on atomic hydrogen have been calculated in the energy range 50 to 1200 keV amu -1 using a classical-trajectory Monte Carlo method. Cross sections for the same processes for Fe q+ ions incident on molecular hydrogen have been measured for q=11-22 at 1100 keV amu -1 , for q=9 at 277 keV amu -1 , and for q=12 and 14 at 262 keV amu -1 . The experimental cross sections for molecular hydrogen divided by two are in excellent agreement with the calculated atomic hydrogen cross sections. Scaling laws for the cross sections with q, the charge state of the incident ion, are discussed. The scaling with q is not found to follow the q 2 law predicted by the binary-encounter theory.