Spectra of the Later Actinides

The absorption spectrum of the hexagonal form of BkCls as a function of time. The changes in the spectrum are due to the formation of CfCF. Note the sharp Tanthanide-like transitions characteristic of the later actinide (-1-3) state, (from J.R. Peterson et al, Inorg. Chem., 1986, 25, 3779 reproduced by permission of the American Chemical Society). 

After the emission of a p-particle from the Bk nucleus the californium ion regains an electron to maintain the (-1- 3) oxidation state  

It may also be noted that crystal type is retained X-ray diffraction confirms that the CfCb retains the hexagonal structure of the original BkCb rather than adopting the orthorhombic modification. 

Uranium(vi) compounds are expected to be diamagnetic, with their Sq (f°) ground state. However, compounds like UFe and uranyl complexes in fact exhibit temperature-independent paramagnetism, explained by a coupling of paramagnetic excited states with the ground state. 

Uranium(v) compounds are, as expected for an f system, paramagnetic, usually exhibiting Curie-Weiss behaviour, with large Weiss constants g-values, expected to be 6/7, are modified by the mixing in of higher states and by orbital-reduction effects (covalency), experimental -values including values of 1.2 in NasUFg and 0.71 in CsUFe. 

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