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An absorption band at 435 nm with a half‐value width of 0.57 eV which causes the yellowish colour of PbMoO4 crystals is due to Pb3+ ions. Pb3+ ions are produced by oxidation of the crystals or by incorporation of foreign cations of oxidation state lower than 6 at Mo5+ sites. Usual Pb3+ ion mole fractions are ⪅ 10−7. Annealing of the crystals at low oxygen partial pressure discolours them. Colourless crystals become coloured at low temperatures by ionizating irradiation causing absorption bands at 380 and 575 nm due to Mo5+ ions and at about 990 nm due to an other electronic centre (may be Pb+ or F centre). Heating causes a thermoluminescence connected with disoloration which is finished at room temperature.
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W. Bollmann (1980) studied this question.
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