5d–4f luminescence of Ce3+, Gd3+ and Lu3+ in LiCaAlF6

The emission and excitation spectra as well as decay kinetics of luminescence due to 5d–4f transitions in Ce³⁺, Gd³⁺ and Lu³⁺ ions doped into LiCaAlF₆ crystals have been analyzed with high spectral and time resolution using synchrotron radiation for excitation. The rich fine structure originating from electronic origins of transitions and their phonon replica has been well resolved and identified. Experimental data are compared with the spectra simulated in the framework of the semiphenomenological models of the crystal field and the crystal lattice dynamics.     

掺杂三价铽离子的碱土金属钨酸盐的光谱特性研究

本文合成了一系列掺杂三价铽离子的碱土金属钨酸盐,测定了晶体的X射线粉末衍射数据及发射光谱和激发光谱.所合成的化合物均属四方晶系,I41/a空间群,晶胞多数随金属离子半径的增大而增大.研究了在这些晶体中三价铽离子5D3→7Fi和5D4→7Fi跃迁发射的激发态及其能量传递机理和浓度猝灭机制.讨论了发射光谱和激发光谱与铽离子浓度、金属离子半径及铽离子在晶体中的溶解度的关系.     

Inelastic quasiparticle lifetimes of the Shockley surface state band on Ni(111)

We present a study of the low-energy quasiparticle lifetimes of the Shockley surface state on the Ni(111) surface with scanning tunnelling spectroscopy. By measuring the coherence length of the decaying standing wave pattern at straight step edges electron and hole lifetimes have been determined. The values of the lifetime measured on this ferromagnetic surface show to be considerable smaller than the values obtained from noble metal surfaces. This is explained by differences in the electron density of states at the Fermi energy but has to include substantial spin-flip scattering. Furthermore hole lifetimes appear to be larger than electron lifetimes with the same excitation energy. Although only results for the majority spin component are presented, a spin-dependent selfenergy is expected.     

CaLuBO4∶Tb^3+荧光粉的制备及发光性质

采用高温固相反应法合成了不同Tb^3+掺杂浓度的CaLuBO4∶xTb^3+荧光粉,研究了样品的晶体结构和发光性质。在紫外光激发下,样品的发射光谱由Tb3+离子的5D3→7FJ(J=6,5,4)和5D4→7FJ′(J′=6,5,4,3)特征发射组成,其中位于545 nm和554 nm附近的5D4→7F5跃迁发射强度最大。荧光粉的激发光谱是由位于紫外区的Tb3+的4f-5d和f-f跃迁构成的。研究了Tb3+浓度对样品发光性质的影响。测量并分析了CaLuBO4∶xTb^3+荧光粉的5D3能级和5D4能级荧光寿命。结果表明,CaLuBO4∶xTb^3+是一种适于紫外激发的新型黄绿光荧光粉。     

Two level metal vapor lasers with thermal creation of population inversion

We present a new technique for direct conversion of thermal energy into coherent radiation. The near-surface layer of evaporated excited atoms of rare earth metals is proposed to be used as a converter. There is an inverted population in this layer. Operation principles of two level lasers on the transitions to the ground state using Eu are considered. The fact of detachment of Sm atoms in the excited 4f(N-1)5d6s2 state during the thermal evaporation process has been proved experimentally.     

Eu原子4f~76p_(3/2)ns自电离态的光谱的研究(英文)

采用孤立实激发技术,对铕原子4f~76p_(3/2)ns(n=7,8)自电离态的光谱进行了系统的研究,同时是首次在不同激光偏振组合下进行的研究。首先,用前两束激光分步将铕原子从基态4f~76s~2经中间4f~76s6p态激发至4f~76sns里德堡态,然后再用第三束激光通过离子实4f~76s~+→4f~76p~+_(3/2)的跃迁将其进一步激发至4f~76p_(3/2)7s自电离态或4f~76p_(3/2)8s自电离态。对铕原子4f~76p_(3/2)ns(n=7,8)自电离态复杂的光谱分别给出了详细的解释,从中我们可以获得一些重要的光谱信息,比如自电峰的能级位置和线宽等,同时还可以观察到收敛于不同离子限的自电离系列之间的组态相互作用。最后,通过比较不同激光偏振组合下的自电离光谱,确定了一些自电离态的总角动量的值。     

Resonant coherent excitation of Ar17+ ions taking into account a fine structure of energy levels

The effect of a fine structure of the orbital electron energy levels of an Ar¹⁷⁺ ion on the resonant coherent excitation under planar channeling has been investigated by computer simulation technique. The obtained resonance curves are characterized by two closely situated peaks due to the transitions of an electron from the ground to excited states corresponding to the different components of a fine structure of the first excited state which differ in the value of the total electron momentum (1/2 or 3/2).     

Tb3+掺杂Y2O3纳米晶体中Tb3+离子4f5d跃迁及能量传递的研究

采用燃烧法制备了不同Tb3 掺杂浓度和不同粒径的Y2O3:Tb纳米晶体粉末样品,并通过高温退火获得了相应Tb3 掺杂浓度的体材料样品。测量了纳米和体材料样品的发射光谱、激发光谱、X射线衍射谱和荧光衰减曲线,并拍摄了不同粒径样品的透射电子显微镜(TEM)照片。研究纳米Y2O3∶Tb晶体粉末中Tb3 离子的4f5d跃迁发现,由于在近表面的低结晶度环境和颗粒内部的高结晶度环境中Tb3 离子4f5d跃迁对应的激发峰位置不同,不同粒径样品中处于这两种环境的Tb3 离子比例也不同,激发谱的谱线形状存在较大差别,还对Tb3 离子的能量传递进行了研究,发现Y2O3∶Tb晶体粉末中Tb3 的(5D3,7F6)→(5D4,7F0)能量传递类型为受纳米限域效应影响很大的电偶极电偶极相互作用;引起5D4→7F5(543nm)发光浓度猝灭的是不同Tb3 离子5D4能级之间交换相互类型的能量传递,此类型的能量传递受纳米限域效应影响较小。     

温度对于掺杂在SrAl12O19中Pr3+4f5d发射的影响

测量了在真空紫外光激发下,SrAl12O19∶Pr3 在不同温度(308~483 K)时的发射光谱,同时观测到了电偶极禁戒的4f2→4f2和电偶极允许的4f5d→4f2跃迁。随温度升高,4f5d→4f2与1S0发射的相对强度逐渐增强。运用Pr3 4f2组态最高的能级—1S0能级和4f5d组态最低能级间的热平衡模型成功解释了SrAl12O19∶Pr3 发射光谱随温度变化的现象。     

钡钇氟化物中Eu2+离子的激发光谱和发射光谱

在298和77K下分别研究BaYF5(BaF2·YF3)中Eu2+的激发和发射光谱。Eu2+的发射光谱中,除了一个属5d-4f跃迁的宽发射带外,还有一组6PJ→8S7/2的4f-4f跃迁窄谱线发射。它们的发射强度与Eu2+的浓度和温度有关。由於Eu2+从4f7基态跃迁到4f65d1态产生两个宽的激发带,4f65d(eg)和4f65d(t2g)。实验证实,Eu2+的6PJ→8S7/2的窄谱线发射主要来自高能级的t2g激发能弛豫的结果。     

Spectroscopy of highly luminescent 1,3,5-triazapentadiene complexes of platinum(II) in solution and in the adsorbed and solid states and quantum-chemical interpretation

We have measured the absorption, luminescence, and luminescence excitation spectra, as well as the excited-state lifetimes and luminescence quantum yields, of 1,3,5-triazapentadiene complexes of platinum(II) in a solution, in the solid state, in an adsorbed state on a SiO₂ surface, and in a polystyrene matrix at room temperature and at 77 K. We also have performed quantum-chemical calculations of the equilibrium geometry of the ground and excited states of the complexes and of the nature and structure of molecular orbitals.     

Intra- and inter-configurational luminescence spectroscopy of Pr3+ -doped YPO4 nanophosphors

Nanopowders of YPO₄ phosphors with different Pr³⁺doping were successfully prepared by a sol gel method under different synthesis conditions. The crystallite size and strain show a strong dependence on the Pr³⁺ doping concentration and on the annealing temperature. By annealing at 300 °C one can obtain the xenotime structure of the pure YPO₄. The crystallite size can be controlled by controlling the annealing temperature and it increases with increasing the annealing temperature. The room temperature inter-configurational 4f² ↔ 4f5d and intra-configurational 4f²↔ 4f² emission-excitation transitions spectra are measured and investigated. Upon 4f² → 4f5d excitation transition, all the samples present broad intense emission bands attributed to 4f5d → 4f² emission transitions and peaks in red region assigned to ¹D₂→³H₄ transition as photon cascade emission phenomena (PCE). The presence of only ¹D₂→³H₄ transition is discussed. In addition, the ¹D₂ energy level lifetimes as well as the refractive indexes were determined and discussed.     

5d-4f luminescence of Nd3+, Gd3+, Er3+, Tm3+, and Ho3+ ions in crystals of alkaline earth fluorides

The vacuum ultraviolet emission spectra of alkaline-earth fluoride (CaF₂, SrF₂, BaF₂) crystals with rare earth impurity ions (Nd, Gd, Er, Tm, Ho) have been investigated. The main luminescence bands are described well by the transitions from the lowest excited 5d state to different 4f levels of rare earth ions.     

Eu原子4f~76p_(3/2)6d自电离过程的动力学特性

采用孤立实激发技术(isolated-core excitation, ICE)及速度影像技术(velocity-map imaging,VMI),研究了Eu原子4f~76p_(3/2)6d自电离过程的动力学特性.孤立实激发技术用于将Eu原子从基态4f~76s~(2 8)S_(7/2)经中间态4f~76s6p激发到4f~76s6d里德堡态,然后将其进一步激发至4f~76p_(3/2)6d自电离态;速度影像技术用于探测其自电离过程的动力学特性,从而获得自电离衰变的分支比(branch ratio, BR)和弹射电子的角分布(angular distribution, AD).自电离衰变的分支比代表离子的能量分布,从中获得VMI影像的径向信息;而通过各向异性参数描述的弹射电子的角分布揭示了VMI影像的角向信息.此外,讨论了自电离衰变分支比和弹射电子角分布在整个自电离共振能域内的变化情况.基于4f~76s~+和4f~75d~+两个离子态的分支比,讨论了实现Eu离子粒子数反转的可能性.     

Ca4LaNbMo4O20:Pr3+荧光粉的发光性质

采用高温固相法成功制备出荧光粉Ca₄LaNbMo₄O₂₀:Pr³⁺,通过X射线衍射分析了样品的结构,其结构与CaMoO₄结构相似。在Ca₄LaNbMo₄O₂₀:Pr³⁺的激发光谱中出现了NbO₄^3-和MoO₄^2-的电荷迁移(CTS)吸收和Pr³⁺离子的4f→4f5d激发跃迁,以及Pr³⁺-金属离子的价间电荷迁移(IVCT)吸收;另外在420~520 nm处,还观测到属于Pr³⁺离子的典型f-f激发跃迁。发射光谱中,在452 nm激发下,主要出现绿光和红光两种发射,其峰值位于490 nm和607 nm处,分别是Pr³⁺的³P₀→³H₄和¹D₂→³H₄的跃迁作用;在紫外287 nm激发下出现NbO₄^3-和MoO₄^2-发射和Pr³⁺离子的4f5d→4f跃迁宽带,以及Pr³⁺离子的4f→4f发射峰。     

Site selective 4f5d spectroscopy of CaF2 : Pr

Spectroscopic investigations were performed on a single crystal of CaF₂ doped with 0.05% Pr³⁺. Three different Pr³⁺ sites with different luminescent properties were identified. The 4f² →4f¹5d¹ excitation spectrum of the first site has a sharp maximum at 221.3 nm. Excitation in the 4f5d bands of this site yields strong 4f5d emissions in the UV/VIS part of the spectrum and also weaker intraconfigurational 4f² emissions. By comparing the intraconfigurational 4f emissions and their decay times with data from the literature, these 4f5d bands are assigned to transitions on Pr³⁺ ions on a site with C_4V symmetry. The fd excitation spectrum of the second site has a zero phonon line at 223.3 nm. Upon selective excitation in this band, only 4f5d emission is observed. Probably, these 4f5d bands correspond to Pr³⁺ ions on a O_h site. The third set of 4f5d bands has a 4f5d onset at 208 nm. By comparison of the luminescence spectra of the intraconfigurational 4f² transitions with literature data, these transitions are assigned to Pr³⁺ on an L site. Excitation in these 4f5d band yields ¹S₀ emission followed by emission from the ³P₀ state. The present results clarify some contradictions reported in the literature.     

Optical transitions of Eu2+ IONS in RbMgF3 crystals

Because of the need for tunable solid state lasers in the blue region of the spectrum, a number of recent studies have been on the optical properties of Eu²⁺ in various crystals lattices. The absorption and emission from Eu²⁺ ions in fluoride hosts arise from both 5d→4f and 4f→4f transitions. The absorption is in the ultra-violet and the emission is in the blue. The 4f-4f transitions are very sharp and are located around 360 nm. The 5d→4f emission bands at 405 nm and 525 nm are broad and host lattice dependent. We have studied the temperature dependence of the optical properties of RbMgF₃:Eu²⁺ including absorption, emission, and excitation. In the case of the emission studies both temperature dependence and the lifetimes of the transitions have been measured. These transitions are discussed in detail.     

Er3+/Yb3+共掺LiNbO3晶体中Er3+的光谱特性分析

在室温下,测量了采用Czochralski方法生长的as-grown和经退火处理的Z切Er^3＋／Yb^3＋共掺同成分LiNbO3晶体的α偏振吸收光谱（300-1650nm）。运用Judd—Ofelt理论对该晶体中Er^3＋的光谱特性进行了分析。由所测得的吸收系数的积分计算得到了从基态到激发态的若干个主要的电子跃迁强度实验值。利用最小二乘法确定出Er^3＋／Yb^3＋共掺LiNbO3晶体中Er^3＋的Judd-Ofelt参数。进而确定了自发辐射概率,从激发态能级到其各个下能级的荧光分支比以及能级辐射寿命。此外,还讨论了Yb^3＋的共掺和退火处理对LiNbO3晶体中Er^3＋光谱特性的影响。     

Optical losses in YVO4: RE (RE = Nd3+, Er3+, Tm3+) laser crystals

The relevance of processes contributing to depletion of pump and upper laser levels has been assessed based on experimental data obtained during measurement of excited state absorption, steady state emission and dynamics of excited states as a function of excitation power and activator concentration. It has been concluded that the excited state absorption in YVO₄: Nd and YVO₄: Er is not significant except for that from the ⁴ I _11/2 level of Er³⁺. In these systems, the interionic processes are dominant. In particular, the reported decrease of the YVO₄: Er laser slope efficiency when the Er³⁺ concentration increased from 0.5 to 1 at % is due mainly to the up-conversion by energy transfer from the pump level and upper laser level. Excited state absorption cannot contribute to depletion of excited states involved in the ³ F ₄-³ H ₆ laser operation near 1800 nm in the YVO₄: Tm crystal. However, the heavy doping required to enhance the cross-relaxation process which feeds the upper laser level brings about the migration-accelerated energy transfer to energy sinks.     

Excitation of transitions terminating at the 4f 12(3 H)5d6s 2(6,3/2) levels of the thulium atom

The excitation of transitions terminating at the 4f ¹²(³ H)5d6s ²(6,3/2) levels of the thulium atom are studied experimentally. Seventy-five cross sections of the TmI spectral lines are measured at an excitation electron energy of 50 eV. Five optical excitation functions are recorded in the electron energy range of 0–200 eV.