title: Comparison of keV N2(+*)/He and N2(+*)/Ar collisions by emission spectroscopy and theory.
abstract: Collision-induced emission spectra from 190-1020 nm were obtained for N 2 (+*)/Ar collisions at laboratory frame collision energies from 2 to 8 keV. The relative emission intensities of N 2 (+*), N (+), and N (*) are independent of the ion translational energy within the studied energy range, supporting the curve-crossing mechanism for collisional excitation. The role of the target gas in keV N 2 (+*)/He and N 2 (+*)/Ar collisions was investigated by both emission spectroscopy and theoretical calculations. Adiabatic potential energy surfaces calculated at the CISD/6-311+G(2df) level of theory for N 2 (+*)/He and N 2 (+*)/Ar collisions indicate that excitation to the A (2)Pi u and B (2)Sigma u (+) states involves curve-crossing first to the C (2)Sigma u (+) state, and the difference in N 2 (+*) emission intensities from the two systems can be accounted for by the slope difference at the crossing points based on the Landau-Zener curve-crossing model.
authors.affiliation: Department of Chemistry, University of Ottawa, 10 Marie-Curie, Ottawa, Ontario, Canada K1N 6N5.
authors.forename: Clement
authors.initials: C
authors.lastname: Poon
authors.forename: Yawei
authors.initials: Y
authors.lastname: Lin
authors.forename: Paul M
authors.initials: PM
authors.lastname: Mayer