FTICR-MS study of the gas-phase thermochemistry of americium oxides

Gas-phase ion chemistry experiments with americium using Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) were performed for the first time. Reactions of Am+ and AmO+ with the oxidants N2O, C2H4O (ethylene oxide), H2O, O-2, CO2, and NO have been studied. Am+ formed AmO+ with all the reagents except NO, while AmO+ only reacted with C2H4O to form AmO2+ and other products. These results allowed us to estimate the previously unknown Am+-O and OAm+-O bond dissociation energies. The ionization energies (IE) of AmO and AmO2 could also be determined by two different types of experiments: charge-transfer "bracketing" with AmO2+, yielding IE(AmO2) = 7.23 +/- 0.15 eV, and AmO+ reactivity with dienes, following a model developed by Helmut Schwarz and coworkers, leading to IE(AmO) = 5.9 +/- 0.2 eV. With this last method, we were also able to resolve the disagreement; between the two literature values for the ionization energy of PuO. (C) 2003 Elsevier Science B.V. All rights reserved.