Mass Spectrometric Measurement Of the Ionization Energies and Cross Sections Of Uranium and Plutonium Oxide Vapors

Abstract

The ionization and dissociation energies of the different uranium and plutonium oxides have been measured by mass spectrometry of molecular beams produced by Knudsen effusion at high temperature. The values obtained constitute a set of self-consistent quantities, which are in agreement with the existing thermodynamic data of these oxides. On the basis of the experimental molecular parameters, general formulas for the ionization and dissociation/ionization cross sections due to electron inelastic scattering have been obtained for collision energies up to about 60 eV. These formulas are sufficiently accurate to calculate the composition of equilibrium vapor mixtures over UO2 and PuO2 from conventional mass spectrometric measurements.

A theoretical study of the ground state and lowest excited states of PuO0/+/+2 and PuO20/+/+2

“…The IE(PuO 2 ) = 6.36 eV computed by CASPT2+SO is in reasonably good agreement with the value of about 6.6 eV estimated by Capone et al 6 It is notable that previously reported values, which are in the range of 9-10 eV. 5,7 This conclusion is clearly validated by the present theoretical results. It should be noted that the discrepancy of 0.5 eV between the computed value of 6.4 eV and the lower limit of 6.9 eV 1 determined from the electron transfer reactions is minor relative to the large correction, >2 eV, to previously reported experimental 5,7 and theoretical 10 values.…”

“…5,7 This conclusion is clearly validated by the present theoretical results. It should be noted that the discrepancy of 0.5 eV between the computed value of 6.4 eV and the lower limit of 6.9 eV 1 determined from the electron transfer reactions is minor relative to the large correction, >2 eV, to previously reported experimental 5,7 and theoretical 10 values.…”

“…A direct spectroscopic determination of IE(PuO 2 ) would definitively resolve this issue. The accuracy of most current computational methods may not be fully adequate to definitively resolve the 0.3 eV discrepancy between the two low-range experimental values for IE(PuO 2 ), 7.03±0.12 eV 1 and ~6.6 eV 6 , but their accuracy is certainly adequate to resolve the ~3-4 eV discrepancy between this lower range and the much higher values obtained from the earlier EI experiments, 9.4 eV 1 and 10.1 eV 5 .…”

RIMS analysis of ion induced fragmentation of molecules sputtered from an enriched U3O8 matrix

“…The M/F ratios in each case consider the UO 2 and UO as two separate parent masses with U as the fragment mass in each case. This treatment of the data is used for simplicity and does not include the full complement of known fragmentation pathways for gas phase UO x molecules [29].…”

A Fock space coupled cluster study on the electronic structure of the UO2, UO2+, U4+, and U5+ species

“…A joint effort of experimentalists and theoreticians is therefore needed to resolve the electronic structure of these systems. An example is the ionization potential ͑IP͒ of the UO 2 molecule, measured as 5.4 eV by Capone et al 2 using the electron impact technique. Theoretical calculations 3 consistently gave a higher value.…”