EPR of Pb+ ions and exchange-coupled Pb+ ion pairs in U.V.-irradiated PbCl2 and PbBr2 crystals

摘要: In PbCl2 and PbBr2 single crystals at low temperatures (< 200 K) three types of paramagnetic centres (to be called A, B C) can created by u.v. irradiation. The A signal in consists five equidistant (35 G) gaussian-shaped lines with a width 15 G. experimental g-value the central component is 2.0665−0.0310 cos2θ θ angle ab plane. ascribed to Pb+-type Pb++ lattice sites. These may occur isolated as well exchange-coupled pairs along axis. positive shift g-values covalent admixtures excited charge-transfer configurations Pb+ (6p) ground state. unusual behaviour A-signal intensity function time irradiation history explained model which photoelectrons are trapped dislocations, from they subsequently released one-phonon interaction, migrate through ions near holes. lifetime 77 K an electron dislocation trap level depth E approximately given (4−0.6E/kT)-1 103 s for 0