ON THE THERMAL IONIZATION OF DIELECTRON CENTERS IN IONIC-CRYSTALS

The energy required for the thermal ionization of pairs of electrons t rapped in ionic crystals by point defects of positive charge ze (z gre ater than or equal to 2) has been evaluated. Utilizing a simple trial function of the form psi = (pi a(3))(-1/2) exp[- r/a] to represent the electron ground state in dielectron centres, it is shown that Lehovec 's previous results (LEHOVEC K., Phys. Rev., 92 (1953) 253) ape reprod uced with an effective extra-charge (z -5/16)e. The parameter a is det ermined by variational calculus. Results are compared with experimenta l data on thermal ionization energy in ZnS and CdS.