Gas-phase oxidation of Cm+ and Cm2+ --thermodynamics of neutral and ionized CmO

Fourier transform ion cyclotron resonance mass spectrometry was employed to study the products and kinetics of gas-phase reactions of Cm (+) and Cm (2+); parallel studies were carried out with La (+/2+), Gd (+/2+) and Lu (+/2+). Reactions with oxygen-donor molecules provided estimates for the bond dissociation energies, D[M (+)-O] (M = Cm, Gd, Lu). The first ionization energy, IE[CmO], was obtained from the reactivity of CmO (+) with dienes, and the second ionization energies, IE[MO (+)] (M = Cm, La, Gd, Lu), from the rates of electron-transfer reactions from neutrals to the MO (2+) ions. The following thermodynamic quantities for curium oxide molecules were obtained: IE[CmO] = 6.4 +/- 0.2 eV; IE[CmO (+)] = 15.8 +/- 0.4 eV; D[Cm-O] = 710 +/- 45 kJ mol (-1); D[Cm (+)-O] = 670 +/- 40 kJ mol (-1); and D[Cm (2+)-O] = 342 +/- 55 kJ mol (-1). Estimates for the M (2+)-O bond energies for M = Cm, La, Gd, and Lu are all intermediate between D[N 2-O] and D[OC-O] - that is, 167 kJ mol (-1) < D[M (2+)-O] < 532 kJ mol (-1) - such that the four MO (2+) ions fulfill the thermodynamic requirement for catalytic oxygen-atom transport from N2O to CO. It was demonstrated that the kinetics are also favorable and that the CmO (2+), LaO (2+), GdO (2+), and LuO (2+) dipositive ions each catalyze the gas-phase oxidation of CO to CO2 by N2O. The CmO 2 (+) ion appeared during the reaction of Cm (+) with O 2 when the intermediate, CmO (+), was not collisionally cooled - although its formation is kinetically and/or thermodynamically unfavorable, CmO 2 (+) is a stable species.