Electron transfer between heterogeneous lanthanides in BaF2 crystals

Highlights: • Forward electron photo-transfer and reverse thermal transfer between lanthanides in BaF₂ crystals has been studied. • Ultraviolet illumination led to the transfer of electrons from 2+ (Eu, Yb, Sm) to 3+ (Ho, Nd, Dy, Tm, Sm, Yb) lanthanides. • The thermal ionization energies to the conduction band are determined from the thermal bleaching curves of absorption bands. • The experimental energies are compared with the estimated energies of the Dorenbos model. -- Abstract: Forward electron photo-transfer and reverse thermal transfer between divalent and trivalent heterogeneous lanthanides in barium fluoride crystals has been studied using optical absorption. In crystals activated by two heterogeneous lanthanides and grown in reducing conditions, one of the lanthanides becomes bivalent whereas the other lanthanide remains trivalent. Illumination of the crystal in the ultraviolet bands led to the transfer of electrons from divalent lanthalides (Eu, Yb, Sm) to trivalent ions (Ho, Nd, Dy, Tm, Sm, Yb). The thermal ionization energies to the conduction band of created lanthanides are determined from the thermal bleaching curves of absorption bands. The experimental energies are compared with the estimated energies of the Dorenbos model.