On the ground of the study of the luminescence spectral properties

the temperature dependence of the intensity

the decay of the luminescence

and the thermoluminescence of PbWO

4

scintillating crystals

combining the results from the theoretical calculations of its electronic structure

a model of the luminescence dynamics of PbWO

4

scintillator is suggested with the fundamental band structure

the states of the excitonic luminescence centers

and the position of the trap levels in the band gap defined. According to the theoretical calculations

the band gap is 4.4eV

consistent with the fact that the 265nm excitation band is corresponding to the band transition. The stronger 310nm excitation band originates from the exciton whose binding energy is 0.41eV. The energy difference between the ground state and the excited state is 2.88eV and 2.38eV respectively for blue (430nm) and green (520nm) emission centers. The thermal activation energy for the blue and green emission centers is 0.18eV and 0.13eV respectively calculated from the temperature dependence of the luminescence intensity. The thermoluminescence curves indicate that several types of electronic traps exist in the band gap with the energy depth of 0.42

0.60

0.65eV and the deepest 1eV or so. With this dynamical model

the luminescence process of PbWO

4

can be fully explained

especially for the causation of the low luminescence efficiency at room temperature because of the strong thermal quenching. On the other hand

according to our study on the luminescence of PbWO

4

annealed in different atmosphere

we suggested that the green emission center is "WO

4

2-

+Oi"where Oi is oxygen interstitial

instead of "WO

3+

F" where F is an oxygen vacancy holding two electrons

and the blue emission center is some kind of combination center with the form of "WO

4

2-

+some intrinsic defects".