Time-Resolved Spectroscopic Study on the Type I Self-Trapped Excitons in Alkali Halide Crystals. I. Emission Spectra and Decay Behavior

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Decay behaviors of Self-Trapped Excitoxu (STE) luminescence categorized into type Iin seven alkali halides, i.e., the o bands in Nail, KBr, RbBr, Kl and Rbl, and the 7Cbands in NaBr and Nal, are studied by using synchrotron radiation pulses from UV-SOR under single-bunch operation. Counting photons over four orders of magnitudereveals that every o band involves a phosphorescent component with a lifetime longerthan 100 ns, in addition to the main fluorescent component. This evidences that the oband originates from the lowest orbital state of the STE. Simultaneous detectionthrough two different time windows discloses a split in the peak energy of the fluores-cent and phosphorescent components. From this result, a slight difference in the loca-tion of the minima is suggested in the adiabatic energy surfaces for a nearlydegenerate singlet-triplet STE pair with the on-center configuration.[seIf-trapped exciton, alkali halide, exchange energy, time-resolved emission spec- ]l trum, synchrotron radiation, off-center effect, luminescencel
社団法人日本物理学会の論文
1992-11-15