Cluster model for complex compounds of hexavalent uranium

We have studied the regular patterns of the change in the electronic transition frequency in low-temperature luminescence spectra of uranyl trinitrate and tetranitrate crystals with alkali metal cations or an NH ₄ ⁺ group as the outer-sphere cations, as a function of the ionization potential of the latter. An analogous study was carried out as a function of the ratio of the concentrations of impurity and matrix for different cations in mixed crystals and solid solutions. Analysis of the results obtained, together with available crystallographic data, allowed us to propose a cluster model for the uranyl complex. The observed regular patterns are also explained from the standpoint of statistical thermodynamics. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 5, pp. 588–591, September–October, 2006.