A guided-ion beam study of the reactions of Xe+ and Xe2+ with NH3 at hyperthermal collision energies

We have measured the absolute cross sections for reactions of Xe+ and Xe2+ with NH3 at collision energies in the range from near-thermal to ∼34 and ∼69 eV, respectively. For Xe+, the cross section for charge transfer, the only exothermic channel, decreases from ∼200 A2 below 0.1 eV to ∼12 A2 at the highest energies studied. The production of NH3+ is the only channel observed below 5 eV, above which a small amount of NH2+ is also formed. In Xe2+ reactions, the main products observed are NH3+ and NH2+. The charge transfer cross section decreases monotonically from ∼80 to ∼6 A2 over the studied energy range. The NH2+ cross section is similar to the charge transfer cross section at the lowest energies, and exhibits a second component above 0.4 eV, with a maximum of 65 A2 at 0.7 eV, above which the cross section decreases to ∼30 A2 at the highest energies studied. At energies above 10 eV, a small amount of NH+ is also observed in Xe2+ collisions. Product recoil velocity distributions were determined at selecte...