Dissociation of N 2 in capture and ionization collisions with fast H + and 2 N + ions and modeling of positive ion formation in the Titan

6 [1] Electron capture and ionization cross sections for protons and nitrogen ions incident 7 on N2 are measured in the energy range 10–100 keV using time of flight (TOF) 8 coincidence counting techniques. In the case of proton impact the formation of N2 + ions 9 dominates for both electron capture and ionization channels at all energies, whereas 10 for N ions, the N2 + formation dominates for electron capture and the dissociative 11 processes for ionization channels. The energy distribution of the fragment products at 12 20 and 100 keV have also been measured for the first time using the TOF method. These 13 cross sections are useful in the simulation of energetic ions and atoms interacting with 14 Titan’s N2-rich atmosphere. Titan resides primarily within Saturn’s magnetosphere where 15 H and N ions are the major ions present along its orbit. It is found that the neutralization 16 of these ions by charge exchange does not occur efficiently above Titan’s exobase, so 17 energetic particles with large gyroradii penetrate primarily as ions. The ionization rate and 18 energy deposition in Titan’s atmosphere by the energetic H ions observed by the Voyager 19 spacecraft are explained with the help of the present measurements.