以间质隔离法研究CH3O分子在p-H2间质中的红外吸收光谱

本研究利用低温间质隔离技术搭配红外光谱仪研究CH3ONO在p-H2间质中的光解产生CH3O。实验观察到位于689.3/694.6cm-1、945.9/951.7cm-1、1041.8cm-1、1224.7cm-1、1235.5cm-1、1347.7cm-1、1365.4cm-1、1427.5cm-1、1519.5cm-1、1522.3cm-1等处的CH3O红外吸收谱线,并分析得出各振动模式分别为电子态E1/2a1对称性的ν6、电子态E1/2a2对称性的ν6、电子态E3/2对称性的ν2、电子态E3/2e对称性的ν6、电子态E1/2e对称性的ν6、电子态E1/2a1对称性的ν5、电子态E3/2对称性的ν2、电子态E1/2对称性的ν2、电子态E3/2e对称性的ν5及电子态E1/2e对称性的ν5。     

一簇金刚石晶格上S~4模型的相变

采用重整化群和累积展开的方法,研究了一簇金刚石晶格上S~4模型的相变,求得了系统的临界点.结果表明:当分支数m=2和m 12时,该系统只存在一个Gauss不动点K~*=b_2/2, u_2~*=0;当分支数3≤m≤12时,该系统不仅有Gauss不动点,还存在一个Wilson-Fisher不动点,并且后一个不动点对系统的临界特性产生决定性的影响.     

稀土离子激活发光材料中能级跃迁的选择定则

能级跃迁的选择定则可用于判别含稀土离子的发光材料中的光吸收、能量传递和发光及非辐射能量弛豫过程是否发生.本研究中,我们根据跃迁所涉及到的电子组态、稀土离子所处格位的对称性、跃迁所涉及到的多重态及晶格振动情况进行了细致地讨论分析.对于光吸收和发射过程,我们得到了和相关文献报道一致的结果,并对有些结果进行了更细致的解释.对...     

甲氧基(CH_3O)的红外吸收光谱研究

为研究甲氧基CH_3O的红外吸收光谱,以Nd:YAG激光器为光源,使用间质隔离法对p-H_2间质中的CH_3ONO进行光解,在光解产物中观测到CH_3O和NO的红外吸收谱.其中CH_3O红外吸收谱线及分析所得的各自振动模式分别为:689.3/694.6 cm~(-1),振动模式为电子态E1/2a1对称性的ν6;945.9/951.7cm~(-1),振动模式为电子态E1/2a2对称性的ν6;1041.8 cm~(-1),振动模式为电子态E3/2对称性的ν2;1224.7cm~(-1),振动模式为电子态E3/2e对称性的ν6;1235.5 cm~(-1),振动模式为电子态E1/2e对称性的ν6;1347.7cm~(-1),振动模式为电子态E1/2a1对称性的ν5;1365.4 cm~(-1),振动模式为电子态E3/2对称性的ν2;1427.5cm~(-1),振动模式为电子态E1/2对称性的ν2;1522.3 cm~(-1)振动模式为电子态E1/2e对称性的ν5.     

Simulation of the fben d transitions of lanthanide ions in YPO4 using quantum-chemical calculations

We constructed an effective one-electron Hamiltonian by using the 4f/5d energies and eigenvectors obtained from the first-principles calculation with the relativistic self-consistent discrete variational Slater software package (DV-Xα). From the effective Hamiltonian, we obtained the crystal-field and spin-orbit interaction parameters for the 4f and 5d electrons of lanthanide ions (Ce³⁺, Pr³⁺, Nd³⁺ and Eu³⁺⁾ doped in YPO₄, and these parameters were used to calculate the 4f^N-4f^N-15d transition. Comparison with experiments shows that the obtained parameters are reasonable and the excitation spectra can be well predicted.     

First-principles study of the local structure and crystal field of Yb2＋ in sodium and potassium halides

The local coordination structures around the doping Yb 2+ ions in sodium and potassium halides were calculated by using the first-principles supercell model.Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb 2+ were calculated to study the effect of the doping on the local coordination structures of Yb 2+.Using the calculated local structures,we obtained the crystal-field parameters for the Yb 2+ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method.The calculated crystal-field parameters were analyzed and compared with the fitted results.     

First-principles study of the local structure and crystal field of Yb2+ in sodium and potassium halides

The local coordination structures around the doping Yb²⁺ ions in sodium and potassium halides were calculated by using the first-principles supercell model. Both the cases with and without the charge compensation vacancy in the local environment of the doping Yb²⁺ were calculated to study the effect of the doping on the local coordination structures of Yb²⁺. Using the calculated local structures, we obtained the crystal-field parameters for the Yb²⁺ ions doped in sodium and potassium halides by a method based on the combination of the quantum-chemical calculations and the effective Hamiltonian method. The calculated crystal-field parameters were analyzed and compared with the fitted results.     

Ca3Sc2Si3O12:Ce3+的第一性原理研究

对Ca₃Sc₂Si₃O₁₂:Ce³⁺共掺杂N^3-、Sc³⁺、Mn²⁺、Mg²⁺和Na⁺进行第一性原理计算,研究不同的电荷补偿对发光中心Ce³⁺的影响．首先利用密度泛函理论构建超晶胞模型对Ce³⁺周围的局部结构进行了优化,然后通过CASSCF/CASPT2 RASSI-SO计算得到Ce³⁺的4f→5d跃迁能量．计算数据与实验光谱相吻合．实验光谱中的一个未知峰值理论分析确认是Sc³⁺替代Si⁴⁺导致的．     

稀土Ce^(3+)/Eu^(2+)离子和点缺陷发光性质的第一性原理研究EI北大核心CSCD

近年来,国内外研究者们开展了一系列关于无机荧光粉中稀土离子和点缺陷发光性质的第一性原理研究。本文简要介绍作者与合作者们在该研究领域开展的工作与取得的结果。首先,简要介绍稀土发光材料第一性原理研究常用方法,主要包括:基于密度泛函理论和超单胞模型的点缺陷计算以及基于波函数多组态相互作用的激发态计算。然后,从点缺陷的热力学稳定性与发光机理研究以及稀土离子4f→5d跃迁模拟与激发光谱指认两个方面,详细阐述了第一性原理计算在Ce^(3+)和Eu^(2+)离子掺杂荧光粉中的具体应用。最后,对稀土发光材料的第一性原理计算研究领域的机遇和挑战进行了简要总结。     

Simulation of the f-d transitions of lanthanide ions in YPO4 using quantum-chemical calculations

We constructed an effective one-electron Hamiltonian by using the 4f/5d energies and eigenvectors obtained from the first-principles calculation with the relativistic self-consistent discrete variational Slater software package （DV-Xα）.From the effective Hamiltonian,we obtained the crystal-field and spin-orbit interaction parameters for the 4f and 5d electrons of lanthanide ions （Ce～（3+）,Pr～（3+）,Nd～（3+） and Eu～（3+）） doped in YPO₄,and these parameters were used to calculate the 4f～N-4f～（N-1） 5d transition.Comparison with experiments shows that the obtained parameters are reasonable and the excitation spectra can be well predicted.