Investigation of matrix effects on the neutral fractions ejected from ion-bombarded, uranium-containing solids using resonance ionization mass spectrometry

Quantifying Uranium Isotope Ratios Using Resonance Ionization Mass Spectrometry: The Influence of Laser Parameters on Relative Ionization Probability

“…In our experiments, the Ga + sputtering of uranium oxides exhibits a dominance of UO and UO 2 species in the sputtered flux as observed by other workers [31,30] and we also confirm the observation of non-resonant photoions in the uranium mass peaks [29]. In contrast with the findings of Goeringer, Christie, and Valiga [31], however, we observe significant resonance ionization of U from U 3 O 8 (resonant to non-resonant signal of >100). Our enhanced signal to noise is derived from single-ion detection sensitivity and the use of a 3-color resonance ionization scheme in which we optimize the laser power to minimize non-resonance ionization while preserving a high ionization probability for U atoms.…”

“…They found that the sputter yield of U atoms ejected from U metal for Ar + , O + 2 , N + 2 beams were 5.3, 0.50, and 0.67 U atoms per incident primary ion respectively. The relatively high sputter yield from argon is as expected considering the relative masses of the incident species [31]. They report a sputter yield of 2 ± 0.5 U atoms/primary ion for Ar + on UO 2 .…”

“…Other workers ( [29,31]) have observed non-resonant ions at the atomic uranium masses while working with uranium oxides, but in several cases did not observe a resonant atomic uranium signals during those measurements. They did observe resonant uranium ions from other uranium-rich targets.…”

“…RIMS has been shown to be a potential tool for quantifying uranium isotope ratios [28,29,30,31,32]. Early approaches used a single pulsed broadband dye laser (0.063 -0.1 nm bandwidth) tuned to a one-color (591 nm), three-photon ionization scheme.…”

“…Previous studies of multiphoton ionization of uranium oxide species by thermal vaporization [29]and ion sputtering [31] caused concern about the yield of U neutral atoms useful for RIMS from UO x matrices. Goeringer, et al studied the relative yields of U + secondary and resonance ions using Ar + ion sputtering (14.5 keV) of uranium metal and oxides and observed that the sputtered neutral atom yield depended strongly on the sample matrix composition.…”