A. Hofstaetter

EPR of radiation induced MoO 4 3- -centres in lead tungstate

Paramagnetic MoO43- impurity centres are created in undoped PbWO4 single crystals by X-ray excitation at liquid nitrogen temperature. The Spin-Hamiltonian data of the axial electron-centre are discussed in a covalent model which takes into account contributions of cation states. Characteristic differences in EPR- and thermoluminescent features of PbWO4 with respect to other scheelite type tungstates can be explained in terms of the lead ion 6s2-configuration.

Temperature dependence of the ground state splitting of Mn2+ in some scheelite type crystals

The EPR spectrum of Mn2+ in CaMoO4, CdMoO4, CaWO4 and SrWO4 has been investigated in the temperature range from 4.2–380 K. Results are given for the Spin-Hamiltonian parametersb20 andb40. They are completed by data forb20 of Mn2+ in SrMoO4 [1] and discussed with respect to resonant vibrations.

Intrinsic hole centres in Cd x Ca1−xMoO4 mixed crystals

Intrinsic hole centres in scheelite-type CdxCa1−xMoO4 mixed crystals are studied by means of EPR. Starting with CaMoO4 the influence of increasing Cd-concentration on the formation of hole centres and the correlation between their thermal decay and emission of thermoluminescence are investigated. Although no intrinsic hole centres were found in CdMoO4 the measurements on the mixed crystals indicate their stabilization in this crystal too.

Pb3+-ions in CaWO4: Temperature dependence of hyperfine interaction

The hyperfine interaction of the (6s)1 electronic configuration of Pb3+ with Pb-207-nuclei (I=1/2) shows a temperature dependent Fermi-contact-term obeying aT4 × Debyeintegral law. This effect is correlated to increasing delocalisation with temperature.

Crystal fields in the point charge lattice of scheelite-type species

Magnitudes of crystal fields at the cation site in scheelites have been calculated numerically and are presented as functions of effective ion charges allowing comparisons between theoretical and experimental investigations.