Time-resolved luminescence of octahedral selenium (IV)

Abstract

Low temperature (T = 10 K) luminescence decay curves of A2SeCl6 (A = Rb, Cs) are recorded which follow optical excitation at λexc = 458 nm applying different pulse lengths between 90 ns and 100 μs. For short excitation pulses a biexponential decay is observed, for pulse widths t exc > 10 μs a single exponential decay occurs. The experimental results can be explained from two rate equations which describe the (de)population of the lowest excited states (of octahedral s2 systems) within the kinetics in a three-level system. The present compounds are obviously examples where thermally nonequilibrated populations of close-lying excited states can be observed within moderate time scales.