4f-5d transitions of Pr3+ in CaF2

The luminescence excitation spectrum of the Pr³⁺ ion in CaF₂ crystals hase been investigated, and new bands at 3950, 3660, 3380, 2740 and 2620 Å have been observed. These bands are found to be concentration dependent.     

第一性原理研究LuAlO3中掺杂Ce3+的4f-5d跃迁性质

通过对基态4f电子采用杂化密度泛函理论方法、对5d激发态采用限制性布居方法,研究了LuAlO₃:Ce³⁺体系4f-5d跃迁的相关性质．结果表明,伴随着4f到5d的跃迁,Ce³⁺与8个最近邻配位O原子的平均键长缩短了0.05 ?,而且Stokes位移计算值与实验值相当吻合．在优化计算得到的LuAlO₃:Ce³⁺体系4f基态局域构型基础上,采用角重叠模型计算了5d能级的晶场分裂,与实验结果吻合较好.     

Absolute line strengths of 74GeH4 near 5 μm

Line positions and absolute line strengths were measured for 23 Q-branch lines of the ν₃ fundamental of ⁷⁴GeH₄ at 295 K, using an infrared tunable diode laser spectrometer. The spectral range covered was from 2109.9658 to 2110.6218 cm^?1. The average standard deviation of the measured line positions was 0.0006 cm^?1 and that of the line strengths was 3.4%. Vibrational transition dipoles were computed from the measured line strengths, which gave 1226 ± 172 cm^?2 amagat^?1 for the ν₃ integrated band intensity.     

Zeeman splitting of a fluorescing level of CaF2 : U6+

Zeeman spectra for a pure electronic transition in the emission from a crystal of CaF₂ : U cooled to helium temperatures are reported for a magnetic field of 7.7 T along principal crystallographic directions. The polarized Zeeman spectra correspond to those of an E → A transition at a centre with trigonal and inversion symmetry.     

Spectra and oscillator strengths of 3p63d9--3p53d10 and 3p63d9--3p63d84p transitions for cobalt-like Sn23+ ion

This paper calculates the spectra and oscillator strengths for highly ionized cobalt-like Sn23+ ions 3p63d9 3p53d10,3p63d9 3p63d84p transitions by using a multi-configuration self-consistent field method program together with the proposed fitting formula.The calculations have a good agreement with observations.     

Identification of Fe4+ and Fe5+ charge-transfer photochromic absorption bands in SrTiO3

Optical absorption and the enhancement and bleaching of Fe³⁺ and Fe⁵⁺ electron paramagnetic resonance in SrTiO₃: Al measured as a function of wavelength and time show that the photochromic absorption bands are due to electron transfer from O^2- valence states to Fe⁴⁺ and Fe⁵⁺. They occur at 2.09 and 2.82 eV for Fe⁴⁺ and at 1.99 and 2.53 eV for Fe⁵⁺.     

Mn2+ paramagnetic resonance and structural phase transitions in Rb2CdCl4

Structural phase transition in Rb₂CdCl₄: Mn²⁺ single crystal has been found near 133 K by EPR, X-ray and optical methods. Octahedral tilt system in the low temperature phase corresponds to the symmetry change D¹⁷_4h → D¹⁸_2h or D¹⁷_4h → C⁶_2h.     

Infrared electronic transitions of Eu+3 in GdAlO3

Infrared ⁷F_O → ⁷F_J electronic transitions are reported for Eu⁺³ in GdAlO₃. The low symmetry of the crystalline field allows the observation, for the first time, of transitions with J = 3, 4, 5 and 6. The spectra are explained by means of a crystal-field model where a C_s term is added as a perturbation to the cubic field in order to take into account the lattice distortion. This model predicts energy levels which are in good agreement with the experimental data.     

Al~(3+)/Mo~(6+)双离子取代ZrV_2O_7中Zr~(4+)/V~(5+)实现近零膨胀

采用固相烧结法制备了Zri_(1-x)Al_(2-x)V_(2-x)Mo_xO_7(0≤x≤0.9),并通过调整Al~(3+)/Mo~(6+)对ZrV_2O_7中的Zr~(4+)/V~(5+)离子替代量来实现近零膨胀,对于较小的x值(x≤0.3),材料保持了与ZrV_2O_7相同的立方相结构.随着Al~(3+)/Mo~(6+)替代量的增加,(Al/Zr)~-和(Mo/V)~+之间的库仑相互作用逐渐加强,这种库仑相互作用导致材料中未发生畸变的立方相晶体结构逐渐减少.当x≥0.7时,材料中立方相晶体结构完全消失.在425-750 K温度区间内,Zr_(0.5)Al_(0.5)M_(0.6)O_7展示出近零膨胀性质(-0.39×l0~(-6)K~(-1)).Zr_(0.5)Al_(1.5)V_(1.5)Mo_(0.5)O_7的低热膨胀性能可能与Al~(3+)/Mo~(6+)对ZrV_2O_7中Zr~(4+)/V~(5+)部分替代引起部分晶体结构发生的畸变及其对未替代部分的晶格结构的影响有关.     

Er3+/Yb3+共掺NaYF4/LiYF4微米晶体的上转换荧光特性

采用水热法成功制备了Er³⁺/Yb³⁺共掺杂的NaYF₄和LiYF₄微米晶体. 通过X射线衍射仪和环境扫描电子显微镜对样品的晶体结构及形貌进行表征. 实验结果表明: 六方相NaYF₄微米晶体为棒状结构, 而四方相LiYF₄微米晶体则为八面体结构. 在近红外光980 nm激发下, NaYF₄:Yb³⁺/Er³⁺和LiYF₄:Yb³⁺/Er³⁺ 微米晶体均展现出很强上转换荧光发射. 且NaYF₄:Yb³⁺/Er³⁺微米晶体的荧光发射强度大约是LiYF₄:Yb³⁺/Er³⁺微米晶体的2倍, 但红绿比明显较低. 根据荧光光谱, 并借助激光光谱学及发光动力学深入探讨基质变化及表面修饰剂乙二胺四乙二酸(EDTA)对荧光特性的影响. 实验结果发现: 影响荧光强度的主要因素是基质环境的局域对称性, 而导致不同红绿比则是由于样品表面较多的EDTA分子所引起. Er³⁺掺杂的NaYF₄和LiYF₄ 微米晶体呈现出很强的绿光发射可被应用于全色显示, 荧光粉和微光电子器件中.     

Simultaneous cw laser oscillation on transitions of Cd+ and I+ in a hollow-cathode He-CdI2 discharge

Continuous-wave laser oscillation has been obtained on four transitions of Cd⁺ and eleven transitions of I⁺ using a hollow-cathode He-CdI₂ discharge as active medium. Laser output characteristics are similar for both Cd⁺ and I⁺ transitions, and simultaneous cw oscillation has been achieved at wavelengths ranging from blue (4416 Å Cd⁺) through green $\text{(}\text{5337}\text{5378}$ Å Cd⁺, 5407 Å I⁺), yellow $\text{(}\text{5678}\text{5761}$ Å I⁺) and orange (6127 Å I⁺) to red (6585 Å I⁺).     

Collision-induced simultaneous transitions in H2+CF4 and H2+SF6 mixtures

The simultaneous transitions of the v₃ fundamental vibrations of CF₄ and SF₆ with the fundamental Q branch and S(1) line of H₂ have been studied for various H₂+CF₄ and H₂+SF₆ mixtures at total pressures up to 185 bars. The integrated intensities are found to be proportional to the partial densities of the gas mixture components. The agreement between experimental and calculated intensities is generally better for the Kihara potential than for the Lennard-Jones potential.     

Paramagnetic Ru5+ and Ru3+ centers in TiO2:Ru

Paramagnetic resonance on TiO₂ single crystals doped with ruthenium have shown the presence of both Ru⁵⁺(4d³) and Ru³⁺(4d⁵) in oxygen octahedral coordination.     

Energy transfer between Ce3+ and Eu2+ in doped KSrPO4

Powder samples of KSrPO₄ doped with Eu²⁺ and Ce³⁺ were prepared by combustion-assisted synthesis. Their structures and photoluminescence spectra were systemically studied. Energy transfer from Ce³⁺ to Eu²⁺ was observed by investigating the optical properties from photoluminescence spectra in Eu²⁺ single doped and Ce³⁺–Eu²⁺ co-doped KSrPO₄. The enhancement of UV excitation is attributed to energy transfer from Ce³⁺ to Eu²⁺, and Ce³⁺ plays a role as a sensitizer. Ce³⁺–Eu²⁺ co-doped KrSrPO₄ powders can possibly be applied as blue phosphors in the fields of lighting and display.     

Ba5SiO4Cl6: Yb3+, Er3+, Li+荧光粉的制备及上转换发光性质研究

本文采用高温固相反应法制备了Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺, Li⁺ 荧光粉, 并对其上转换发光性质及其发光机理进行了研究. 在980 nm 激光的激发下, Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺ 荧光粉呈现较强的红色(662 nm) 和较弱的绿色(550 nm) 的上转换发光, 红色和绿色的上转换发光分别对应于Er³⁺ 离子的⁴S_3/2/²H_11/2→⁴I_15/2 和⁴F_9/2→⁴I_15/2 跃迁, 且随着掺杂的Er³⁺ 和Yb³⁺ 离子浓度增加, 样品的上转换发光强度增加, 这是因为Yb³⁺ 离子和Er³⁺ 离子之间的能量传递效率增加引起的. 在0.5—0.8 W 功率激发下,样品属于双光子发射, 而在0.9—1.2 W 功率激发下样品具有新的上转换发光机理——光子雪崩效应. 探讨了Li⁺ 掺杂对Ba₅SiO₄Cl₆: Yb³⁺, Er³⁺ 样品的上转换发光性质的影响, Li⁺ 离子的掺杂引起Ba₅SiO₄Cl₆:Yb³⁺, Er³⁺ 上转换发光强度增加, 这是由于Li⁺ 离子的掺入降低了晶体场的对称性引起的.     

5at％Yb3＋：YNbo4的提拉法晶体生长和光谱特性

用提拉法生长了新型激光晶体5at％Yb3＋：YNbO4,测量了它的吸收和光致发光光谱,计算了它的吸收和发射截面,并对其激光性能进行了评估．Yb3＋：YNbO4的吸收半峰全宽为17nm,吸收峰位于933,955,974和1003nm,相应的吸收截面分别为0．73×10^-20,1．85×10^-20,0．86×10^-20。和0．44×10^-20cm2;最大吸收截面值为Yb3＋：YAG的两倍．光致发光谱的发射带的中心位置处于1020nm附近,相应的半高宽为41nm,是Yb3＋：YAG的3倍;Yb3＋：YNbO4在955,974,1005,1021和1030nm处都有着较大的发射截面,截面值分别为0．69×10^-20,0．86×10^-20,1．81×10^-20,1．11×10^-20和0．57×10^-20cm2,最大发射截面值与Yb3＋：YAG相当．Yb3＋：YNbO4晶体的宽发射带有利于实现相应波长的超短脉冲和可调谐激光输出,表明它是在这些领域非常有希望的全固态工作物质．     

Dye laser site selection spectroscopy on U6+ luminescent molecular centers in LiF-U3O8 crystals

The polarized excitation and emission spectra of the U⁶⁺ molecular centers giving the most intense emission lines at 18 940 cm^?1 and 19 285 cm^?1 are presented and analyzed in detáil. From the polarization experiments, it is shown that the symmetry of the centers is C_4v and that the symmetries of the observed electronic states are Γ₂, Γ₁ and Γ₅. Finally, an electronic model is proposed which associates the emission and excitation lines of the U⁶⁺ centers in the visible region to transitions between the fundamental state $\text{Γ}{}_1\text{(6p}{}^6\text{,}{}^1\text{S)}$ and the states of the excited configuration $\text{6p}{}^5\text{(}{}^2\text{P}\text{3}\text{2}\text{) 7s}$.     

Crystal-field anisotropy of Sm3+ in SmCo5

It is shown that the major contribution to the high uniaxial anisotropy of the compound SmCo₅ arises from the action of crystalline and exchange fields on the Sm³⁺ ion.     

Al~(3+)掺杂ScVO_4∶Eu~(3+),Bi~(3+)荧光粉的制备及发光性质

采用高温固相法在1 000℃下煅烧6 h合成了Sc VO4∶Eu3+,Bi3+,Al3+荧光粉。使用X射线粉末衍射仪和扫描电镜对样品的结构和形貌进行了表征,采用荧光分光光度计研究了样品的发光性质。用315 nm波长激发Sc VO4∶Eu3+,Bi3+,Al3+样品时,样品在590~620 nm范围内发射强烈的橙红光,最大发射峰位于615nm。少量Al3+的掺入可以增强Sc VO4∶Eu3+,Bi3+荧光粉的发光,而掺入过量Al3+时会使Sc VO4∶Eu3+,Bi3+荧光粉的发光变弱。当Al3+在Sc VO4∶Eu3+,Bi3+中的摩尔分数达到4%时,样品的发光最强且其发光强度较未掺杂Al3+的样品提高了约30%。