| Budget Amount *help |
¥1,650,000 (Direct Cost: ¥1,500,000、Indirect Cost: ¥150,000)
Fiscal Year 2007: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2006: ¥1,000,000 (Direct Cost: ¥1,000,000)
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| Research Abstract |
Previously, Azumi investigated the phosphorescence emission from hexanuclear molybdenum duster, and concluded that the phosphorescence is composed of three spin sublevels that are originated from the splitting due to spin-orbit coupling. Sometimes later, Grey, et. al. reported several hexanuclear rhenium dusters and concluded that the emission is composed of a number of vibrationally excited triplet states. In this work, splitting due to spin-orbit coupling was not at all considered. On the other hand, Kitamura, et. al. analyzed similar hexanuclear rhenium clusters in terms of spin-orbit-coupling-induced spin sublevels. However, different from the Mo duster's case, they concluded that the emission is composed of four, not three, spin sublevels. Here, the nature of the spin sublevels has not been clarified. Since all of these molybdenum and rhenium clusters have identical number of d-electrons and have identical symmetry, why the emission mechanisms differ is puzzling.
In order to clarif
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y this point, we have newly investigated series of hexanuclear molybdenum and rhenium clusters in various counter ions and also with variety of halogen ligands.
From the series of experiments, a lot of meaningful information has been obtained. (1)all the molybdenum dusters and rhenium dusters exhibit almost identical temperature dependence on lifetimes and emission peak (2)The observations in PMMA polymer matrices indicate that the emission is completely independent of counter ions, and the emission properties are only determined by the central duster ions alone.
Detailed analysis of the temperature dependence of lifetime and of emission peak clearly indicate that the phosphorescence is composed of three spin sublevels that are resulted from the spin-orbit coupling. Further by extending the observed temperatures to such a low temperature as 3 K, the Jahn-lbller distortion and the resulting energy splitting of the second lowest spin sublevels has been clarified.
In the theoretical part of the work, we have concluded that the double group theory based on only d-electrons of transition metal ions can be widely and successfully applied to this sort of metal clusters. Less
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