Kinetics of Ultrafast Migration-Accelerated Quenching in Nanoparticles

It has been analytically shown that the kinetics of ultrafast migration-accelerated quenching of luminescence in nanoparticles for the case of the short-pulse-induced excitation of donors has a complex multistage character. This conclusion has been confirmed by Monte Carlo computer simulation. An order stage (exponential in time) has been observed at small times. However, in contrast to a bulk crystal, quenching in nanoparticles is exponential only to a depth determined by the average number of donors in nanoparticles. Then, differences in the quenching rates of excitations in individual nanoparticles lead to the onset of a disordered stage of ultrafast quenching, which satisfies a t 3/S time law for the S multipole interaction type. The quenching rate of excitations at the disordered stage depends on the average number of donors in nanoparticles. In this property, ultrafast quenching in nanoparticles qualitatively differs from that in a bulk crystal: the ultrafast quenching rate in the bulk crystal is independent of the donor subsystem parameters as a whole and the donor concentration in particular. The time of the transition between stages has been determined.