Nanosecond reverse saturable absorption in cubanelike transition-metal clusters

We report the measurement of reverse saturable absorption in four cubanelike transition-metal clusters with nanosecond laser pulses. We also present a five-level rate-equation model in which ionization and germinate recombination are included. A comparison between the model and the measured data shows that the population of the triplet states is generated mainly through the ionization–recombination process, and triplet–triplet absorption is responsible for the measured reverse saturable absorption.