Cooperative optical phenomena in praseodymium doped CsCdBr3

In CsCdBr3 the trivalent Rare-Earth (RE) ions substitute for the divalent Cd ions. For reasons of charge compensation and the specific crystal structure, RE centers of the form RE3+ - (Cd vacancy) - RE3+ are preferentially formed. These symmetric pair centers are very suitable for studying cooperative effects of RE ions. These include processes between the ions of the pair as well as processes between the coupled pair and the electronic excitations of the host lattice. Experiments will be shown and discussed on: (i) cross relaxation and up-conversion by direct ion-ion interaction; (ii) cooperative cross relaxation of the Pr3+ pairs with the host lattice; and (iii) cooperative vibronic emission of the Pr3+ pairs with high phonon progressions.