| Autor: |
Ard SG; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States., Sweeny BC; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States., Lewis TWR; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States., Long BA; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States., Viggiano AA; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States., Shuman NS; Air Force Research Laboratory, Space Vehicles Directorate, Kirtland Air Force Base, Kirtland, New Mexico 87117, United States. |
| Abstrakt: |
Kinetics of the lanthanide cations (Ln + = La + -Lu + excluding Pm + ) reacting with molecular oxygen were measured in a selected-ion flow tube apparatus from 300 to 600 K. Where exothermic, these reactions occur efficiently, producing LnO + + O. The reactions display positive temperature dependences consistent with Arrhenius equation behavior and show small activation energies (0-2 kJ mol -1 ) that are strongly correlated to promotion energies of the Ln + atoms. Reanalysis of literature data on neutral Ln + O 2 reactions show a similar correlation with slightly larger activation energies (0-10 kJ mol -1 ). The data are explained by a common mechanism controlling oxidation by molecular oxygen in these systems, as well as in gas-phase reactions of transition metal and posttransition metal cluster anions, neutral clusters deposited on surfaces, and for oxygen incident on metal surfaces. It is posited that across these systems, the height of an early barrier along the reaction coordinate is predictable based on knowledge of the electronic states of the reactants and may be used to either promote or inhibit oxygen activation. |
