Electron-transfer collisions of low-energy multicharged nitrogen ions with H2 and N2

A stored-ion collision technique has been used to study the charge-changing collisions of multicharged nitrogen ions with H₂ and N₂ target gases. The ions were produced inside a Penning trap with use of electron-impact ionization. The time constants for exponential ion loss by charge-changing collisions were measured at several target-gas densities, and from these time constants and densities the rate coefficients for electron capture were calculated. For the collision of N³⁺ with H₂, for which calculations by Gargaud and McCarroll were available, the cross section for electron capture was obtained from the rate coefficient using v¯, where v¯ is the rms ion velocity. The relationships of the other measurements to available theory and to ion-beam measurements at higher energies are discussed. Rate coefficients were obtained at mean ion energies near 1.1, 1.65, and 2.3 eV for N^q+ charges q of 2, 3, and 4, respectively. The results of the rate coefficient determinations are k(N²⁺,H₂)=[7.8(1.2)]×10^-10 cm³/s, k(N³⁺,H₂)=[5.4(0.8)]×10^-11 cm³/s, k(N⁴⁺,H₂)=[4.2(0.6)]×10^-10 cm³/s, k(N²⁺,N₂)=[2.6(0.3)]×10^-9 cm³/s, k(N³⁺,N₂)=[3.5(0.4)]×10^-10 cm³/s, and k(N⁴⁺,N₂)=[2.0(0.3)]×10^-10 cm³/s.