Investigation of Spin States of Excited Triplet States by a Newly Developed Double Group Theory

Azumi先前研究了六核钼粉的磷光发射，得出了磷光由三个自旋亚能级组成的结论，这些自旋亚能级是由自旋轨道耦合引起的分裂产生的。后来，Grey等人报道了几个六核铼粉尘，并得出结论，发射是由许多振动激发的三重态组成的。在这项工作中，完全没有考虑自旋轨道耦合引起的分裂。另一方面，Kitamura等人根据自旋-轨道耦合诱导的自旋亚能级分析了类似的六核铼团簇。然而，与Mo粉尘不同的是，他们得出的结论是，发射是由四个而不是三个自旋亚能级组成的。在这里，自旋亚能级的性质尚未得到澄清。由于所有这些钼和铼簇具有相同数量的d电子和相同的对称性，为什么发射机制不同是令人困惑的。为了进一步阐明这一点，我们在不同的反离子和不同的卤素配体下研究了一系列六核钼和铼簇。从这一系列的实验中，获得了许多有意义的信息。(1)钼粉尘和铼粉尘对寿命和发射峰的温度依赖性几乎相同(2)PMMA聚合物基体中的发射完全不受反离子的影响，发射特性仅由中心粉尘离子决定。对寿命和发射峰温度依赖性的详细分析清楚地表明，磷光是由自旋轨道耦合产生的三个自旋亚能级组成的。进一步，通过将观测温度扩展到3 K这样的低温，澄清了简-伊勒畸变和由此产生的第二低自旋亚能级的能量分裂。在本文的理论部分，我们得出结论：仅基于过渡金属离子d电子的双群论可以广泛而成功地应用于这类金属团簇。少

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 … More 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