摘要
We have proposed that under suitable conditions there exists the phenomenon of elec-tron transfer between a pair of trivalence rare earth ions whose electronic configurations areconjugate （e.g. Eu-Ce, Eu-Tb, Ce-Yb, etc.） to realize stable electronic configurations (4f<sup>0</sup>,4f<sup>7</sup> and 4f<sup>14</sup>) and make the valenee state of rare earth ions changed. For example,
基金
Project supported by the National Natural Science Foundation of China.
