Optical studies on nucleation and nanoparticle growth

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By using the space-resolved, time-resolved and selective excitation spectroscopic methods, we have studied the nucleation and nanoparticle growth of various kinds of clusters and nanoparticles ;(1) alkali metal and rare-earth metal clusters in noble gas : Na, K, Rb, Sm, Eu and Yb,(2) nanoparticles in superionic conductor glasses : (AgI)_x-(AgPO_3)_<1-x>,(AgI)_x-(Ag_2Mo_4)_<1-x> (M : Mo, W) and(3) luminescent clusters in rare-earth oxide solid : Eu_2O_3.The following results are obtained.(1) alkali metal and rare-earth metal clusters in noble gasThe emission spectra indicating the excitation energy transfer between vapour species, energy pooling and radiation trapping in alkali metal vapour zones are clearly observed.(2) nanoparticles in superionic conductor glassThe photoluminescence and excitation spectra indicate the nucleation and nanoparticle growth the superionic conductor glasses with increasing AgI concentration, and also give important information on the electronic states between the nanoparticles and glass matrix.(3) luminescent clusters in Eu_2O_3Under irradiating a CW UV laser light at room temperature in vacuum and oxygen gas atmosphere, the film, microcrystals and powder compact of Eu_2O_3 exhibit a reversible photoluminescence (PL) spectral change between a red sharp-line structure and a white broad one. The reversible phenomena to be observed are interpreted as the results of both the valence-number change of europium ions (Eu^<3+> → Eu^<2+>) and the luminescent clusters combined oxygen vacancies and Eu^<2+> ions.