Investigations of the optical band positions,EPR parameters and defect structure for the trigonal Cr3+–Li+ centre in CsMgCl3 crystal

A unified calculation of optical band positions and electron paramagnetic resonance (EPR) (or spin-Hamiltonian) parameters for the trigonal Cr³⁺–Li⁺ centre in CsMgCl₃ crystal is made by using the complete diagonalisation (of energy matrix) method based on the two-spin–orbit-parameter model. In this model, the contributions from the spin–orbit parameter of central dⁿ ion and that of ligand ion are included. From the calculation, the 11 observed optical and EPR data (eight optical band positions and three EPR parameters g_//, g_⊥, D) are reasonably explained with five adjustable parameters and the defect structure of the Cr³⁺–Li⁺ centre (which is consistent with the expectation based on the electrostatic interaction) in CsMgCl₃ is acquired. The results are discussed.     

Thermal Behavior of the Fluorescence Lines of Ho3+ in Cr,Tm,Ho:YAG

The fluorescence spectra of Cr,Tm,Ho:YAG crystal have been detected at the temperature from 65 to 295 K with interval of 10 K. The width and the shift of Ho3+ lines at 4959.6 cm-1 (at 65 K) have been investigated and interpreted in terms of the interactions between lattice vibration (phonons) and ions. The results showed that the line broadening with the temperature was mainly due to the Raman scattering of phonons,and the line shift with temperature was mainly due to the emission and absorption of virtual phonons.     

Optical spectroscopy of Cr3+ and Rh2+ in sodium-beta-̋alumina

Ion exchange techniques were used to substitute Cr³⁺ and Rh²⁺ ions for the sodium ions present in sodium-beta″-alumina single crystals. The optical absorption and fluorescence spectra were obtained and the fluorescence lifetimes measured for both types of samples. In each case the emission consisted of two bands having significantly different decay times. The temperature dependences of the fluorescence intensities and lifetimes were measured for these bands. The results are interpreted in terms of the energy level structures of these ions in different crystal field sites in this host lattice and the diffusion of ions in the conduction plane which changes these sites.     

Cr3+:GGG(Ca,Mg,Zr)和Nd3+,Cr3+:GGG(Ca,Mg,Zr)激光晶体的光谱特性

本文分析了Cr3+:GGG(Ca,Mg,Zr)的荧光谱和吸收谱,测算到Cr3+离子在4T2g-2Eg的能级间距为ΔE≈70cm-1,晶场强度Dq/B=2.50.说明由于GGGa(Ca,Mg,Zr)晶格扩大减弱了晶场,可望实现Cr3+:GGG(Ca,Mg,Zr)室温下的调谐及Nd3+:Cr3+:GGG(Ca,Mg,Zr)中Cr3+→Nd3+能量的转移.最后从理论上阐明了Cr3+在晶体GGG(Ca,Mg,Zr)中的能级结构.     

Thermal Behavior of the Fluorescence Lines of Ho~(3 ) in Cr,Tm,Ho∶YAG

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Eu3+∶Sm3+∶Cr3+∶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Eu3 ∶Sm3 ∶Cr3 ∶YAG ,其直径达到54mm ,荧光色坐标为x=0 .6 137,y =0 .3738,相当于波长λ=599nm的红色荧光 ,具有较高的色饱和度。这种单晶材料具有很好的抗电子束灼伤能力 ,在入射能量达到 10 5W/m2 时无发光猝灭现象 ,是一种较理想的红色单晶荧光材料。     

多相基质中Cr3+→Nd3+能量传递

根据分相成核原理，通过一步热处理过程，制备了双掺杂B2O3－Al2O3-SiO2系统透明玻璃陶瓷，XRD分析确定主晶相为莫来石固溶体；分别测定了材料的吸收光谱，发射光谱和荧光寿命，分析讨论了铬和钕格位分布及光谱特点，在双掺杂铬和钕玻璃陶瓷中存在较强的Cr^3 →Nd^3 的辐射能量传递和无辐射传递，Cr^3 主要位于晶相格位中，Nd^3 则全部保留在剩余玻璃相中，Cr^3 的格位分布对光谱性能有很大的影响。     

Relaxation phenomena in Cr3+ doped Al2O3−Fe 2 57 O3 systems

Mössbauer absorption spectra have been measured for Cr³⁺ doped Al₂O₃?Fe ₂ ⁵⁷ O₃ systems for different values of the Cr³⁺ concentration at room temperature. The cross relaxation between Fe³⁺ and Cr³⁺ ions, which destroys the paramagnetic hyperfine structure of Fe⁵⁷ observed in undoped Al₂O₃?Fe ₂ ⁵⁷ O₃, is thoroughly studied. The experimental results suggest a new kind of cross-relaxation process involving three spins, i.e. two Fe³⁺.ions and one Cr³⁺. The process, though it is a higher-order one, is highly effective because it is energy-conserving.     

掺Cr3+玻璃陶瓷光谱特性

采用分析纯原料,利用分相成核制备了利用性良好的掺Ｃｒ＾３＋Ｂ２Ｏ３－Ａｌ２Ｏ３－ＳｉＯ２系透明玻璃陶瓷;测定了材料的吸收光谱和发射光谱,分析了讨论了光谱特性。     

Jahn–Teller effect in the 4T2g excited state of Cr3+ ion in Cs2NaYF6 crystal

Calculations of the fine structure of Cr³⁺ energy levels in Cs₂NaYF₆ accompanied by estimations of the Jahn–Teller (JT) stabilization energy in the first excited ⁴T_2g state of Cr³⁺ ion are presented. Two independent approaches—effective second-order spin–orbit Hamiltonian and analysis of the potential energy surfaces—are used. The JT energy was estimated to be 216 and 257 cm^–1 in the first and the second models, respectively. It is shown that the octahedral [CrF₆]^3? complex undergoes an equatorial expansion by 0.09 Å and an axial elongation by 0.02 Å due to the combined effect of the a_1g and e_g normal modes.     

KCdF3晶体中Cr3+-Li+中心局域结构研究

利用零场分裂参量与晶体结构之间的定量关系,研究了双掺杂晶体KCdF3∶Cr3+,Li+的局域结构.指出,对于 KCdF3∶Cr3+,Li+晶体,四角晶场的形成包含两个方面:(1)由于电荷补偿而产生的等效电荷形成的四角对称晶场;(2)Cr3+的局域结构发生晶格畸变而产生的四角对称晶场.事实上,当Cr3+和Li+掺入KCdF3晶体时,Cr3+代替了Cd2+离子;由于Cr3+离子与Cd2+离子的半径不同、电荷不同、质量不同,导致Cr3O+的局域结构发生晶格畸变,由此而产生四角对称晶场;由于电荷补偿,Li+ 离子取代了[001]方向与Cr3+离子邻近的Cd2+离子,由此产生的等效电荷而形成的四角晶场.这样,Cr3+的局域结构由Oh对称变为C4v点对称 .文中建立了ZFS参量和晶体结构之间的定量关系.在考虑晶格畸变和等效电荷的基础上,研究了KCd F 3∶Cr3+,Li+晶体的ZFS参量,理论结果和实验符合很好.得到了F-离子向中心离子分别移动为ΔR1=0.00268nm,ΔR2=0.001nm,ΔR3=0.00165nm .     

Ce3+离子敏化Eu3+∶Cr3+∶Sm3+∶YAG外延层的荧光现象

对Ce3+ ∶Eu3+ ∶Cr3+ ∶Sm3+ ∶YAG处延层中的荧光敏化现象进行了报道和分析 ,在较高浓度的Ce3+ 离子掺杂时 ,外延层在蓝色、绿色波段出现了新的荧光谱线 ,可解释为在Ce3+ 离子敏化作用下 ,Eu3+ 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Ce3+ ∶Eu3+ ∶Cr3+ ∶Sm3+ ∶YAG外延层还是一种新颖的白色单晶荧光材料。     

Resonant structure due to the 3p→3d transition in the photoionization of Ca+

Many-body perturbation theory has been used to calculate the resonance structure (3p→3d) into the photoionization (4s→kp) for ion Ca⁺. This resonance structure results from the interference between a photoionization process or a photoionization with excitation process and a resonant Auger process. The coupled equation method has been improved to calculate this interference by the summation of specific classes of diagrams of perturbation theory to infinite order. The resonance structure in the region of the 3p threshold is enhanced via a super-Coster–Kronig transition. The theoretical results are in good agreement with experiment.     

Cr3+在SrTiO3晶体中的晶场能级

由激发光谱及荧光光谱的测量,运用Tanabe-Sugano能量矩阵计算了Cr3+在SrTiO3晶体中的晶场能级.     

Efficient Cr3+ sensitized Nd3+: GdScGa-garnet laser at 1.06 μm

Room-temperature cw lasing at 1.061 m has been obtained in Cr,Nd: GdScGa-garnet. Threshold powers as low as 7 mW and slope efficiencies up to 41% have been measured. Cross pumping of Nd³⁺ via Cr³⁺ is nearly as efficient as direct pumping. Time-resolved measurements of the transfer rate yield a transfer efficiency of 0.86 and an average transfer time of 17 s. An improvement in pulsed broad band pumping can also be expected.     

ZnWO4:Cr3+晶体的光谱

采用提拉法生长出不同掺杂浓度的ZnWO4:Cr3+单晶.该材料在912nm处形成宽带荧光发射.激发峰随掺杂浓度的加大而向短波方向移动.在发射带晶体的吸收低,有可能作为在800-1000nm可调谐激光工作介质.     

Higher rotational lines in the ν2 fundamental of the H3+ molecular ion

By use of a new high-pressure hollow-cathode discharge cell and a Fourier transform spectrometer, many lines of the ν₂ fundamental band of H₃⁺ are observed in emission. These lines are discriminated from those of other species by pressure labeling, in which the relative intensities are studied as functions of the H₂ gas pressure in the cell. The H₃⁺ lines are found to persist to higher pressures than those of H atoms or H₂ or H₃ molecules. Practically all of the previously known lines of H₃⁺ are observed with this cell, and the measurements are extended to higher J because of the high rotational temperature of the H₃⁺. Absorption measurements of some high-J lines were also performed in this new cell. Altogether 113 lines of the ν₂ band of H₃⁺ with J′_max = 10 have been assigned, and 111 of them are fitted to 0.0654 cm⁻¹ with a 29-parameter effective Hamiltonian that uses a Padé formulation of the centrifugal distortion effects. Many of the higher rotational levels of ν₂ are affected by a Birss resonance with levels of ν₁. The fitted values ν₁ = 3175.0 cm⁻¹ and α₁₂ = 1.377 cm⁻¹ for the vibrational frequency and perturbation parameter are in reasonable agreement with ab initio values. Alternative fits using a vibration-rotation supermatrix model with a limited number of independent matrix elements are consistent with these assignments, but the quality of these fits degrades rapidly with increasing J′_max because the model does not describe centrifugal effects accurately.     

Photoacoustic spectra of Fe3+ and Cr3+ in lithium chromo-ferrites,Li0.5Fe2.5−xCrxO4 (0≤x≤2.5)

Photoacoustic spectra of polycrystalline Li_0.5Fe_2.5−xCr_xO₄ (x=0, 0.5, 1.25, 2.0 and 2.5) and LiFeO₂ have been investigated at 300K in the wavelength range 200–2500 nm. The spectra of x=0 composition arises from octahedral and tetrahedral Fe³⁺ ions in the spinel lattice. The Crsubstituted Li-ferrite phases exhibit broad maxima in the range 1400–1600nm and these are attributed to tetrahedral Cr³⁺ present in these phases besides the usual octahedral Cr³⁺ ions. The results are discussed in the light of recent work on tetrahedral Cr³⁺. The results of ferrimagnetic resonance spectra of Li ferrites and their Cr-substituents are also reported and correlated with photoacoustic spectra.     

Upconversion Luminescence of Eu3 + in NaYbF4∶ Tm3 + , Eu3 +Nanocrystals Induced by 980 nm Excitation

利用水热法制备得到NaYbF4∶0.01％Tm3+,20％ Eu3+上转换材料,利用X射线衍射分析、扫描电子显微镜及光谱测试技术分别对其进行了结构、形貌以及光谱性质的表征.在980 nm近红外激光激发下,得到了Eu3+的可见到紫外范围的上转换荧光发射.分析表明:共掺杂NaYbF4纳米材料中Tm3+到Eu3+离子的能量传递对布居Eu3+离子的激发态能级,获得Eu3+的上转换发光起着至关重要的作用.另外,在实验中首次获得了Eu3+对应于3P0→7Fj(j=0,1,2)能级跃迁的上转换光发射.