Thorium ionization energy

Neder H, Heusser G, Laubenstein M (2000) Low-level y-ray germanium-spectrometer to measure veiy low primordial radionuclide concentrations. ApplRadiat Isot 53 191-195 Palacz ZA, Freedman PA, Walder AJ (1992) Thorium isotope ratio measurements at high abundance sensitivity using a VG 54-30, an energy-filtered thermal ionization mass spectrometer. Chem Geol 101 157-165... 

If reasonable amounts of negative quarks could be had in a sample, energetic photons just above the threshold can ionize the quark to a free state with moderate kinetic energy. One advantage of such an experiment liberating photo-ionized quarks is that a high-resolution spectrometer (or related multi-channel device) can detect the well-defined X-rays emitted by the capture of the quark to a definite heavy atom (such as gold or thorium). 

Quantum electrodynamic (QED) effects are not included in the present work. A recent calculation of these effects for s electrons [66] gave estimates of about 0.04 eV for the ionization potential of the Tl + 6s electron (self energy 0.05 eV, vacuum polarization —0.01 eV) and 0.06 eV for the El 11 Is electron (self energy 0.09 eV, vacuum polarization —0.03 eV). Since the p electrons responsible for the transitions discussed in this work exhibit much weaker penetration into the nucleus, QED effects here are expected to be considerably smaller, at most 0.01-0.02 eV, within the error limits of the method ( 0.05 eV) estimated by comparing calculated and experimental results for thorium (Tables 2.5 and 2.6). 

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