High-resolution triple-resonance autoionization of uranium isotopes

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

“…The laser wavelengths are tuned to excite two resonance transitions and an autoionizing state to selectively ionize neutral uranium atoms within the sputtered flux. The 3-color, 3-photon RIMS scheme for uranium atoms used herein was adapted from work by Schumann et al [14] and is described in detail by Isselhardt and co-workers [15]. The resonantly ionized uranium atoms are then extracted into a reflectron-type TOF-MS at +2 kV and focused onto a MCP ion detector.…”

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

“…The narrow resonance marked with an asterisk is described in the text. (Reproduced from Schumann, et al [51]) that corresponds to a lifetime of ∼ 3 ns, which is very long for an autoionizing state, indicating weak coupling between the discrete state and the ionization continuum. The two autoionizing resonances explored in this work, including the sharp long-lived state just discussed and the very broad peak just above 49, 974 cm -1 , are identified by arrows in the spectrum and will be further described in the experimental details of the resonance ionization scheme.…”

“…It has been shown that the energy shifts of the individual F states follow a pattern of energy separation that is a consequence of their angular momenta components (F, I, and J) and the details of the atomic structure of a given isotope (mass and volume differences that lead to the isotope shift). The energy shifts for individual hyperfine states can be calculated from the Casmir Formula [51,52]: 56) where…”

“…The calculated C-G coefficients for this transition are included in Appendix C. Figure 2.9 is an atomic energy level diagram of 235 U showing the 8 non-degenerate angular momentum states created by the inclusion of nuclear spin in the ground and first excited levels considered in our resonance ionization scheme. The individual F states are shown along with their energy in MHz relative to the average energy of the level, and are calculated by the Casmir formula with the empirically measured constants of Schumann, et al [51]. Each state of total angular momentum F will have a set of (2F + 1) degenerate magnetic substates and thus there are 21 unique transition energies allowed by the selection rules for linearly polarized light.…”

“…The main focus of our work employed the scheme from Schumann, et al [51] that uses three resonant steps (3-photons) where each transition utilizes a different wavelength (3-colors of light). We also examined a 2-color, 2-photon scheme outlined in the work of Ray, et al [68].…”