Guided ion beam investigation of the reaction CO++CO: C–O bond activation and C–C bond formation

Abstract

We have investigated six different endothermic channels in the reaction of CO + ions with neutral CO. For each ionic product we have measured the kinetic energy dependence of the integral cross section and inferred the neutral products by the reaction energetics. The onset of the process producing C + , O, and CO, has been identified by a feature of the integral crosssection located at about 8.5 eV. Measurements of the product isotopic ratio suggest that C + originates from both the CO + ion and the neutral CO molecule. For the reaction channels producing C 2 + + O 2 and C 2 O + + O respectively, measurements of the reaction thresholds allow us to estimate the heats of formation of these two ionic products, ∆ f H 0 (C 2 +) = 19.8 ± 0.2 eV and ∆ f H 0 (C 2 O +) = 14.7 ± 0.2 eV. These values are in good agreement with recent independent estimations. Finally, we re-evaluated the dissociation energy of C 2 + (X 4 Σ g-), D 0 (C +-C) = 6.2 ± 0.2 eV.

Bond-forming reactions of dications: Production of ArO+ and ArO2+ in the reaction of Ar2+ with O2

“…16,17 Briefly, the Ar 2ϩ beam is produced by electron bombardment of Ar at 65 eV, at a relatively high pressure to reduce the production of excited dications Ar 2ϩ *. The electron energy is high enough to produce Ar 2ϩ ions not only in the ground 3 P but also in the low-lying excited states ( 1 D, 1 S); however, the fraction of these excited Ar 2ϩ * ions should be small, as they are expected to be quenched by collisions with neutral Ar.…”

Bond-forming reactions of molecular dications with rare gas atoms: Production of ArC2+ in the reaction CO2++Ar

“…The experiments were performed in a modified version of a guided-ion beam tandem mass spectrometer which has been described before. [20][21][22] The CO 2ϩ reactant ions are produced by electron impact of CO using an electron beam at 85 eV. Ions are extracted from the differentially pumped ion source, mass selected by a magnet mass spectrometer, and finally injected into a radio-frequency octopole ion guide 23 which is surrounded by the reaction cell.…”

C N bond formation in the reaction of nitrogen ions N + with benzene molecules

“…and lying at even masses; there is also a small contribution from C n H m fragments containing a 13 C carbon atom, whose e ect can be eliminated knowing the natural abundance of 13 C. Thus, the reaction of C 6 D 6 with 15 N ions leading to CAN bond formation yields peaks at odd masses which are shifted by 1 a.m.u. when the primary ion beam is switched from 14 N to 15 N . Moreover, the combination of measurements using C 6 D 6 or C 6 H 6 and 14 N = 15 N provides information about signal backgrounds and makes possible a cross-check of the experimental results.…”

“…1, is a guided ion beam tandem mass spectrometer that has been described previously [15]. Nitrogen ions, produced by electron impact of N 2 in a di erentially pumped ion source, are mass-selected by a magnetic mass spectrometer and subsequently injected into a radio-frequency octopole ion guide [16] which passes through the reaction cell containing benzene at about 10 À5 mbar.…”

“…For example, the signal due to H 2 C 5 N which appears in the mass spectrum at a mass± charge ratio m=q 76 is completely hidden by the more intense C 6 H 4 signal at the same m=q ratio. To extract the signal of interest, we therefore use a suitable combination of isotopically labelled reactants, 15 N and C 6 D 6 . Pure hexadeuterated benzene yields a fragmentation pattern that is dominated by a sequence of peaks, with a spacing of two atomic mass units (a.m.u.)…”