Evidence for energy transfer induced by superexchange in LaF 3 : Pr3+

Direct measurement of fluorescence quenching rates for various Pr 3+ pairs in weakly doped LaF3 are reported. Since few pairs only are quenched, the transfer mechanism is short range. From the rate values, the shape of the fluorescence decay for heavily doped samples is predicted. The good agreement with the observed decay proves the interest of the connection between microscopic and macroscopic measurements. Finally arguments are developed to prove that the transfer mechanism is superexchange.