Institute for Solid State Physics, The University of Tokyo, 5-1-5 Kashiwanoha, Kashiwa, Chiba 277-8581, Japan.
J Chem Phys. 2013 Aug 28;139(8):084303. doi: 10.1063/1.4818809.
Resonant couplings of the electronic states and the stretching vibrations of CN(-) ligands, which bridges metal ions, is investigated by resonance Raman spectroscopy for Rb(0.94)MnFe(CN)6·0.2H2O. Large excitation wavelength dependences over one order of magnitude were found for Raman peaks corresponding to different valence pairs of metal ions in the excitation wavelength range between 350 and 632 nm. In the thermal low-temperature phase, the CN(-) stretching modes due to the low-temperature-phase configuration (Fe(2+)-Mn(3+)) and the phase-boundary configuration (Fe(3+)-Mn(3+)) are coupled to the Fe(2+)-to-Mn(3+) intervalence transfer band and Jahn-Teller distorted Mn(3+) d-d transition band, respectively. In the photoinduced low-temperature phase, the Fe(3+)-Mn(3+) mode shows strong resonant enhancement with the CN(-)-to-Fe(3+) charge-transfer band, which exists in the high-temperature phase with a cubic structure. From these resonance behaviors, we conclude that the local lattice symmetry of the photoinduced phase is cubic in contrast with the tetragonal symmetry in the thermal low-temperature phase.
通过共振拉曼光谱研究了桥连金属离子的 CN(-)配体的电子态和伸缩振动的共振耦合，该光谱用于 Rb(0.94)MnFe(CN)6·0.2H2O。在 350 到 632nm 的激发波长范围内，发现对于对应于金属离子不同价对的拉曼峰，其 Raman 峰的激发波长依赖性很大，达到一个数量级。在热低温相中，由于低温相结构（Fe(2+)-Mn(3+)）和相界结构（Fe(3+)-Mn(3+)），CN(-)伸缩模式分别与 Fe(2+)-到-Mn(3+) 价间转移带和 Jahn-Teller 畸变 Mn(3+)d-d 跃迁带耦合。在光诱导低温相中，Fe(3+)-Mn(3+)模式与 CN(-)-到-Fe(3+)电荷转移带表现出强烈的共振增强，该电荷转移带存在于具有立方结构的高温相中。从这些共振行为中，我们得出结论，与热低温相的四方对称相比，光诱导相的局部晶格对称是立方的。
