Annealing induced absorption phenomena in PbWO4

Annealing experiments with the PWO samples in atmospheres with various contents of oxygen have shown that for the centers absorbing at 343, 360, 420 nm, and in the very broad and shallow absorption band around 800 nm, the presence of oxygen is necessary for their function as absorption centers. When the oxygen is annealed out of the centers, their absorption ability disappears. The 343 nm absorption center is proposed to consist of a vacant WO3–molecular complex and an oxygen atom occupying the complex.