Quantum mechanical single configurational coordinate (QMSCC) calculations have been performed on model phosphor systems. Variation of the QMSCC parameters provides information about the influence of these parameters on the temperature dependence of the luminescence efficiency. The results of the calculations are correlated with experimental results reported in the literature.

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In this paper we report on the luminescence properties of three selectively excited uranate centers in sodium fluoride crystals, viz. the (UO6⋅VF)×, (UO6⋅VF)×p and (UO5F)× centers. The emission transition is assigned to a 4γ7u→12γ8u transition. The emission spectra and the lowest energy band in the excitation spectrum show vibronic patterns associated with two electronic origins due to splitting of the excited electronic states under C4v symmetry. The relative intensities of the two vibronic patterns are temperature dependent. The temperature dependence of the decay time of the luminescence of the three uranate centers provides information about the transitions involved in the luminescence processes. An analysis of the vibrational structure in the luminescence spectra is presented.

In this paper the excitation spectra of the luminescence of the octahedral uranate group (UO6−6) are presented for various uranium-doped compounds. The excitation bands have been assigned using the results of theoretical and experimental investigations into the spectroscopic properties of uranium hexafluoride which is isoelectronic with the octahedral uranate group. Charge transfer transitions from orbitals having mainly oxygen 2p character to orbitals having mainly uranium 5f charcter have been observed in the region 2.24–∼4 eV. Charge transfer transitions to orbitals having mainly uranium 6d character have been observed at 4.4 eV and at 5.4 eV.

Luminescence and electrical conductivity measurements on uranium‐activated sodium‐fluoride single crystals are reported. By varying the preparation procedure of the crystals the emission spectra of four different uranium centres can be isolated. The electrical conductivity of the crystals increases with increasing uranium content and appears to depend on the growth conditions. In crystals that have been grown in a nitrogen atmosphere the extrinsic conductivity is governed by sodium‐ion vacancies, while in the air‐grown crystals fluoride‐ion vacancies constitute the conducting species in the extrinsic region. From the results a model is deduced for the configurations of the uranium centres. The centres contain hexavalent uranium and can be represented by (UO6)', (UO5F)x, and (UO4F2).. At low temperatures ion vacancies are associated with effectively charged uranate centres.