Hi all, I need your help. What can be reason of strong increase in the luminescence efficiency of other rare earth element in combination with introduction of lanthanum to this combination. It is known that the element of lanthanum is can’t be center of the luminescence(La3+ possesses a relatively stable empty 4f shell). There are several reports of this so that La3 + (lanthanum) can be used to sensitize other rare-earth ions. The reason?