Observation of 5f intermediate coupling in uranium x-ray emission spectroscopy

Abstract

The first observation of Intermediate Coupling effects in the occupied 5f states has been made using x-ray Emission Spectroscopy (XES). In the past, the impact of Intermediate Coupling of the 5f states in actinides has long been observed and quantified, using x-ray Absorption Spectroscopy (XAS) to probe the unoccupied 5f states, providing great insight into the enigma of 5f electronic structure. However, no measure of its effects in the occupied states had been reported before this. Moreover, because the 5f occupied states in UF 4 are almost completely of 5f 5/2 character, the observed effect in XES is twice that in XAS for UF 4 .

Towards the Quantification of 5f Delocalization

“…There is a very large enhancement of the 5f peak in the M 4 spectrum, versus that in the M 5 spectrum. This figure is similar to that of Figure 1 in [30]. The details of the normalization are available in [30].…”

“…This figure is similar to that of Figure 1 in [30]. The details of the normalization are available in [30].…”

“…However, there now appears to be a solution to this "blind spot." Recently, it has been shown that the M 4,5 X-ray Emission Spectroscopy of UF 4 [30] exhibits results consistent with the Intermediate Coupling Model of van der Laan and Thole [22]. Normalizing to the 6p → 3d peaks, it can be seen that there is a tremendous differential in the intensities of the 5f peaks in the two spectra, a factor of 5.…”

“…[22] Normalizing to the 6p → 3d peaks, it can be seen that there is a tremendous differential in the intensities of the 5f peaks in the two spectra, a factor of 5. Figure 4 (The X-ray Emission Spectroscopy (XES) results for UO2 are very similar to those of UF4 [30] and are omitted here.) It has been shown that this is consistent with the almost pure n5/2 nature of the two 5f electrons in UF4 and strong, albeit not complete, adherence to electric dipole select rules.…”

“…The sample used was the same as used in earlier studies [2,3]. Uranium samples can be affected by oxidation and sample corruption, but these were not a problem here, as described earlier [30].…”