Cr5+ in SrTiO3: An example of a static Jahn-Teller effect in A d1 system

The effect of uniaxial stress on the EPR spectrum of Cr⁵⁺ in SrTiO₃ has been studied. It is concluded that SrTiO₃:Cr⁵⁺ is a static Jahn-Teller system. The strain-coupling coefficient V₂ is found to be 2 × 10⁴ cm^?1. Our results show that in the absence of external stress the intensity ratio of the EPR lines, at temperatures below the cubic-to-tetragonal phase transition, is related to the macroscopic strain, present in SrTiO₃ at these temperatures.     

V4+ in SrTiO3: A Jahn-Teller impurity

EPR results of V⁴⁺, with $\text{S =}\text{1}\text{2}$, in SrTiO₃ are reported. The tetragonal local symmetry of the impurity ion is related to strong T_2g × ?_g coupling as evidenced by intensity variations in the presence of stress. At 4.2 K the V⁴⁺ EPR behaviour is related to the intrinsic local strain in SrTiO₃.     

Magnetic field effects on the fluorescence of Cr3+ in GdAlO3

The fluorescence spectrum of Cr³⁺ in GdAlO₃ has been examined at 4.2 K as a function of magnetic field up to 60 kG. The resulting splitting of the ²E → ⁴A₂ emission lines are explained in terms of a modified molecular field approximation, which incorporates the effect of the spin fluctuations. The exchange constant in the relaxed excited state is found to be 1.2 cm^-1, which differs from that reported from absorption data. It is suggested that the difference may be related to the Frank-Condon effect.     

KMgF3:Cr3+的EPR参量和K+空位研究

EPR和ENDOR表明:顺磁离子取代KMgF₃中的Mg²⁺离子后,所处的环境具有轴对称。本文研究了KMgF₃:Cr³⁺的Δg=g_∥-g_⊥和零场分裂值D,证实KMgF₃:Cr³⁺中K⁺空位的存在。并且指出:由于K⁺空位,使Cr³⁺的最近邻F^-离子分 关键词：     

Temperature dependence of the local mode in the vibronic spectrum of SrTiO3:Cr3+

The local vibrational mode exhibited by chromium impurity ions in strontium titanate has been investigated using vibronic spectroscopy. The temperature dependent characteristics of the mode are attributed to anharmonic interactions with lattice phonons. Line broadening contributions are made by both a decomposition mechanism and inelastic phonon scattering. Elastic phonon scattering processes can explain the line shift while multiphonon emission causes the integrated intensity to decrease. The results are compared with previous local mode investigations made on alkali halides by i.r. absorption spectroscopy.     

Observation of low frequency lattice vibration modes in the vibronic spectrum of SrTiO3:Cr3+

Complicated structure is observed in the vibronic sideband appearing on the high energy side of the zero-phonon lines of chromium doped strontium titanate at low temperatures. The most intense peaks can be associated with specific low frequency lattice vibration modes at different parts of the Brillouin zone.     

KZnF3:Cr3+和KMgF3:Cr3+四角对称电子顺磁共振参量与晶格缺陷的研究

用Newman叠加模型研究了KZnF₃:Cr³⁺四角对称基态的零场分裂,证实了Zn²⁺空位和畸变的存在;并指出,空位对晶场的贡献不可忽略。计算得到:KZnF₃:cr³⁺晶体[0,01]方向的一个F^-配体向Cr³⁺移动Δ(KZnF₃)=0.0029-0.0043nm。还研究了KMgF₃:Cr^{3+关键词：}     

Thermal conductivity of KMgF3 : Cr2+

Observations of resonant scattering of thermal phonons Cr²⁺ ions in KMgF₃ are presented. The results are interpreted with the cluster model of Fletcher and Stevens.     

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⁺.     

Resonant cross-relaxation between Cr3+ and V3+ in Al2O3

Cross-relaxation, which occurs when a V³⁺ transition is resonant with a monitored Cr³⁺ transition, leads to a marked reduction of the spin-lattice relaxation time of Cr³⁺ in Al₂O₃. Measurements and an analysis of the temperature dependence of this effect give a value of 8.34 ± 0.49 cm^?1 for the zero-field splitting of V³⁺, an ion which is strongly coupled to the lattice.     

ESR of Fe3+ -Rhombic,Fe2+ -Vo and Fe1+ -Vo complexes in SrTiO3

Three new Fe-defect complexes have been identified by ESR in Fe doped crystals of SrTiO₃. These are an Fe³⁺ center with rhombic fine structure in the “as-grown” crystals, and the vacancy associated complexes Fe²⁺ -V_o and Fe¹⁺ -V_o in “reduced” crystals. Photo-excited charge transfer effects are observed for these centers.     

KZnF3:Cr3+ — A tunable solid state NIR-laser

Pulsed laser operation at room temperature and cw laser output below 260 K has been demonstrated with the laser material KZnF₃:Cr³⁺ in the spectral range between 775—826 nm. The system can be tuned by dispersive elements in the resonator or by temperature variation.     

Eu^3＋：Sm^3＋：Cr^3＋：YAG红色单晶荧光体

报道外延生长的多激活中心掺杂的红色单晶荧光体Ｅｕ＾３＋：Ｓｍ＾３＋：Ｃｒ＾３＋：ＹＡＧ,其直径达到５４ｍｍ,荧光色坐标为ｘ＝０．６１３７,ｙ＝０．３７３８,相当于波长λ＝５９９ｍｍ的红色荧光,具有较高的色饱和度。这种单晶材料具有委好的抗电子束灼伤能力,在入射能量达到１０＾５Ｗ／ｍ＾２时无发光猝灭现象,是一种较理想的红色单晶荧光材料。     

Nd:Sr5(VO5)3F Q-Switched Lasers with Cr4+:YAG

The Cr4+-doped saturable absorber Cr4+:YAG is used as the passive Q-switch for a conventional pulsed Nd:Sr5(VO5)3F(Nd:S-VAP) oscillator, and the short high-peak-power pulses of laser have been obtained. The laser output characteristics are investigated under the conditions of different small-signal transmittance of Cr4+:YAG and different reflectivity of the output coupler. The rate equtions of Q-switched coupling wave are given, and the numerical solutions of equations are in agreement with the experimental results.     

Ce^3＋离子敏化Eu^3＋：Cr^3＋：Sm^3＋：YAG外延层的荧光现象

对Ce^3 :Eu^3 :Cr^3 :Sm^3 :YAG外延层中的荧光敏经现象进行了报道和分析，在较高浓度的Ce^3 离子掺杂时，外处层在蓝色、绿色波段出现了新的荧光谱线，可解释为在Ce^3 离子每化作用下，Eu^3 离子产生了由高位激发态能级^5Di(i=1,2,3）直接到基态能级^7Fj(j=0,1,2,3）的辐射跃迁过程，并且这种Ce^3 :Eu^3 :Cr^3 :Sm^3 :YAG外延层还是一种新颖的白色单晶荧光材料。     

调谐激光晶体Cr3+:ZnWO4光致发光特性的研究

研究了调谐激光晶体Ｃｒ³⁺：ＺｎＷＯ₄的光致发光特性。报道了它的吸收光谱、激发光谱、发射光谱及其随温度的变化、零声子跃迁和发射寿命等实验结果，并讨论了激发特性、电子－声子耦合作用、ＺｎＷＯ₄中Ｃｒ³⁺的发射寿命曲线等相关问题。 关键词：     

BeAl2O4:Cr3+的晶场能级

金绿宝石中镜对称格位上Cr³⁺(Ⅱ)离子的⁴T₂,⁴T₁和²E能级与该材料的激光运转有关。⁴T₂和⁴T₁能级各分裂成三个子能级。为从偏振吸收谱上确定BeAl₂O₄:Cr³⁺的能级图,本文计算了⁴T₂和⁴T₁的分裂,找到了对谱方法,得到了表征能级分裂的参量K_{1和K2的值。最后给出了以低点群不可约表示标号的、BeAl2O4:Cr³⁺(Ⅱ)的晶场能级图。 关键词：}     

Cr3+/Tm3+/Ho3+共掺氟磷酸盐玻璃的制备及性能表征

制备了不同 Al(PO₃)₃含量的掺铥系列氟磷酸盐玻璃,研究了其结构、热稳定性和光谱性质. 研究了不同摩尔百分数 Al(PO₃)₃掺杂下 Cr³⁺/Tm³⁺/Ho³⁺共掺氟磷酸盐玻璃在 2.0μm 处的发光特性. 并且用Judd-Ofelt理论计算了强度参量,并由此计算了激发能级的自发辐射跃迁速率、辐射寿命、荧光分支比等光谱参量. 结果表明,随着 Tm³⁺浓度增加,2.0μm 处发光的强度逐渐增强. 证明了Tm³⁺(³F₄) →Ho³⁺(⁵I₇)能量转移是非常有效的,并与掺杂浓度有关. 关键词： 氟磷酸盐玻璃 能量传递 荧光光谱 吸收光谱     

Doping effects of Nb5+ on red long afterglow phosphor CaTiO3:Pr3+

A series of Nb5+ codoped red long afterglow phosphors CaTi1 xNbxO3:Pr03.+002 (0 ≤ x ≤ 0.05) is prepared by a solid state reaction method. Their photoluminescence, phosphorescence and thermoluminescence are investigated. The results indicate that codoping Nb5+ can improve the photoluminescence and phosphorescence property of CaTiO3:Pr3+ significantly. When 3-mol% Nb5+ is codoped, the emission intensity of CaTiO3:Pr3+ is enhanced twice, while the afterglow time is extended from 10 min to about 40 min. Thermoluminescence results reveal that the trapping level of CaTiO3:Pr3+ is reduced from 0.82 eV to 0.62 eV by codoping Nb5+. The effect of Nb5+ doping on enhancing the photoluminescence intensity and afterglow time of CaTiO3:Pr3+ is discussed.     

Asymmetry of the splitting of the fluorescence spectrum of Cr3+ in GdAlO3

The fluorescence spectrum of Cr³⁺ in the antiferromagnet GdAlO₃ consists of four broad bands whose peak energies are not perfectly equidistant. A theory recently proposed for the splittung of the fluorescence of a magnetic impurity in a magnetic matrix accounts for the small asymmetry observed.