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Raman spectra of the products It is well-known that Raman spectra are an important tool for identifying the lattice dynamics and the crystal electric field splitting of rare-earth hexaborides。 Fig 8 shows Raman spectra of RB6 nanocubes and nanoparticles,respectively。According to group theory, the hexaboridess tructure has a Pm3m cubic symmetry,which contains A1g+Eg+T1g+T2g+2T1u+T2u vibrational modes, where A1g, Eg, and T2g are Raman activephonons。The A1g and Eg modes originate from the stretching vibration of B–B bonds and T2g is due to the valence angle bending of B–B–B in the boron lattice。 It can be seen that the sespectra are shifted along the vertical direction,and the order corresponds to the decrease of the lattice constants of RB6 from the top to bottom。 However,the peaks of Raman spectra of the same compound of RB6 nanocubes and nanoparticles remain unchanged in the present experiment。The three expected main peaksare observed around680cm_1 (T2g), 1140cm_1 (Eg) and1260cm_1 (A1g), which are inagreement with earlier reports [32–34], and they completelysatisfy the polarization selection rule in the cubic symmetry。 These three prominent peaks are additional confirmation for the formation of hexaborides because the peaks obey these lection rule for the hexaborides’cubic symmetry。 Abroad peak around 1400cm-1, labeled as *, is commonly observed with a relatively strong intensity for trivalent and intermediate-valent crystals。 For trivalentcase,twice the energy of T2g is slightly lower than the peak energy,however,the peak energy systematically follows twice the energy of T2g。 In LaB6, the peak energy is far from twice the energy of T2u and that of T2g is very close to the peak energy。For SmB6 the energy coincidence is very good。Thus it can be concluded that the peak observed in the trivalent case originates from these cond-order process of T2g。 |
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Raman spectra of the products 样品的拉曼光谱研究 It is well-known that Raman spectra are an important tool for identifying the lattice dynamics and the crystal electric field splitting of rare-earth hexaborides。 众所周知，拉曼光谱分析是识别稀土六角硼化物晶体动力学和晶场分裂的重要手段。 Fig 8 shows Raman spectra of RB6 nanocubes and nanoparticles,respectively。 图8分别给出了RB6纳米管和纳米颗粒的拉曼光谱。 According to group theory, the hexaboridess tructure has a Pm3m cubic symmetry,which contains A1g+Eg+T1g+T2g+2T1u+T2u vibrational modes, where A1g, Eg, and T2g are Raman activephonons。 根据群论，硼化物结构具有立方对称的Pm3m空间点群，包括A1g+Eg+T1g+T2g+2T1u+T2u这样一些振动模，其中A1g, Eg, and T2g是拉曼活性的声子模。 The A1g and Eg modes originate from the stretching vibration of B–B bonds and T2g is due to the valence angle bending of B–B–B in the boron lattice。 A1g和Eg模来源于B-B键的拉伸振动，T2g来源于硼晶格中B-B-B键角的弯曲振动。 It can be seen that the sespectra are shifted along the vertical direction,and the order corresponds to the decrease of the lattice constants of RB6 from the top to bottom。 从图的上面往下看，拉曼谱在竖直方向上发生移动，其移动程度对应于RB6晶格常数的减小 However,the peaks of Raman spectra of the same compound of RB6 nanocubes and nanoparticles remain unchanged in the present experiment。 但是，实验中，RB6纳米管和纳米颗粒的拉曼峰却没有发生变化。 The three expected main peaksare observed around680cm_1 (T2g), 1140cm_1 (Eg) and1260cm_1 (A1g), which are inagreement with earlier reports [32–34], 正如所期待的那样，三个主要的拉曼峰出现在 680 m_1 (T2g), 1140cm_1 (Eg) and1260cm__1 (A1g)，这和早先的文献报道一致。 and they completelysatisfy the polarization selection rule in the cubic symmetry。 并且他们完美吻合立方对称结构的极化选择规则。 These three prominent peaks are additional confirmation for the formation of hexaborides because the peaks obey these lection rule for the hexaborides’cubic symmetry。 这三个突出的峰，更加证实了六角硼化物结构的形成，因为这些峰遵从这些六角立方对称性的选择定则 Abroad peak around 1400cm-1, labeled as *, is commonly observed with a relatively strong intensity for trivalent and intermediate-valent crystals。 对于3价或中间价位的晶体，通常在在1400cm-1,标记为 *的地方通常会出现一个较强的宽峰。 For trivalentcase,twice the energy of T2g is slightly lower than the peak energy,however,the peak energy systematically follows twice the energy of T2g。 对于3价情况，T2g的双倍能量比起该峰的能量稍小，这个峰能量系统地紧随T2g能量的两倍值。 In LaB6, the peak energy is far from twice the energy of T2u and that of T2g is very close to the peak energy。 在LaB6中，峰能量比起T2u的2倍能量要小很多。但是T2g的2倍能量去很接近峰能量。 For SmB6 the energy coincidence is very good。Thus it can be concluded that the peak observed in the trivalent case originates from these cond-order process of T2g。 对于SmB6，能量的符合也非常好。因此，可以得出结论，在3价情况下观察到的峰来源于T2g的cond-order过程。 |
2楼2009-12-18 10:54:19
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