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1.
In this paper, the equilibrium geometry, harmonic frequency and dissociation energy of S2^- and S3^- have been calculated at QCISD/6-311++G(3d2f) and B3P86/6-311++G(3d2f) level. The S2^- ground state is of 2IIg, the S3^- ground state is of 2B1 and S3^- has a bent (C2v) structure with an angle of 115.65° The results are in good agreement with these reported in other literature. For S3^- ion, the vibration frequencies and the force constants have also been calculated. Base on the general principles of microscopic reversibility, the dissociation limits has been deduced. The Murrell-Sorbie potential energy function for S2^- has been derived according to the ab initio data through the least- squares fitting. The force constants and spectroscopic data for S2^- have been calculated, then compared with other theoretical data. The analytical potential energy function of S3^- have been obtained based on the many-body expansion theory. The structure and energy can correctly reappear on the potential surface. 相似文献
2.
低温陈化超声波共沉淀法制得SO42-/ZrO2-La2O3前驱体, 经H2SO4处理, 在不同温度下焙烧得到纳米晶催化剂SO42-/ZrO2-La2O3;用Hammett指示剂法测定其酸性. 用XRD、BET、TEM、IR和XPS对样品进行表征,其催化活性用醋酸和甘油的酯化反应进行了评价. 结果表明经超声波搅拌和低温(-15 ºC)陈化,650 ºC焙烧4 h得到的固体超强酸表现出较高催化活性. 相似文献
3.
采用改进的坩埚下降法成功地生长了Tm/Yb共掺氟化钇锂单晶. 该单晶体具有每吸收一个蓝色光子并能发射出2个1000 nm近红外光子的下转换发光效应. 测定了样品的激发光谱、发射光谱和荧光衰减曲线. 在465 nm蓝光激发下观察到由Yb3+:2F5/2→2F7/2能级跃迁所致的960~1050 nm 波段的发射带,此发光带源于Tm3 对Yb3 离子的能量下转换过程. 应用Inokuti-Hirayama模型,研究了晶体的能量转换过程,结果表明Tm3 向Yb3 的能量传递是一个电偶极子相互作用机制过程. 当Tm3 与Yb3 离子的掺杂浓度为0.49mol%与5.99mol%时,单晶的量子剪裁效率达到最大值167.5%. 相似文献
4.
Ho^3+ : GdVO4 is a new laser material suitable for high-power laser systems. In this paper we measure the absorption spectra of Ho^3+ in the sample Ho^3+: GdVO4. The intensity parameters are calculated by using the Judd-Ofelt theory. Some predicted spectroscopic parameters, such as the spontaneous radiative transition rate, branching ratio and integrated emission cross section are dealt with. And we also compare the optical parameters with those of other materials. From these results, it is found that there are many transitions which have large oscillator strengths and large integrated emission cross sections. Especially the transitions such as ^5 F4 → ^5 I 8, ^5 S2→^5 I8, ^5 F5 → ^5 I8 and ^5 I7 →^ 5 I8 are useful in solid-state lasers and other fields. Finally, we discuss the splitting of the energy levels of Ho^3+ in the crystal GdVO4 based on the group theory. 相似文献
5.
采用高温固相法制备了Ca2SiO4:Dy3+发光材料.在365nm紫外光激发下,测得Ca2SiO4:Dy3+材料的发射光谱为一多峰宽谱,主峰分别位于486nm,575nm和665nm处;监测575nm发射峰,测得材料的激发光谱为一多峰宽谱,主峰分别位于331nm,361nm,371nm,397nm,435nm,461nm和478nm处.研究了Dy3+掺杂浓度对Ca2SiO4:Dy3+材料发射光谱及发光强度的影响,结果显示,随Dy3+浓度的增大,黄、蓝发射峰强度比(Y/B)逐渐增大,利用Judd-Ofelt理论解释了其原因;随Dy3+浓度的增大,Ca2SiO4:Dy3+材料发光强度先增大,在Dy3+浓度为4 mol%时到达峰值,而后减小,根据Dexter理论其浓度猝灭机理为电偶极-电偶极相互作用.研究了电荷补偿剂Li+,Na+和K+对Ca2SiO4:Dy3+材料发射光谱的影响,结果显示,不同电荷补偿剂下,随电荷补偿剂掺杂浓度的增大,Ca2SiO4:Dy3+材料发射光谱强度的演化趋势相同,即Ca2SiO4:Dy3+材料发射峰强度先增大后减小,但不同电荷补偿剂下,材料发射峰强度最大处对应的补偿剂浓度不同,对应Li+,Na+和K+时,浓度分别为4mol%,4mol%和3mol%.
关键词:
白光LED
2SiO4:Dy3+')" href="#">Ca2SiO4:Dy3+
发光特性
电荷补偿 相似文献
6.
通过拉曼散射光谱,吸收光谱,荧光发射寿命和808 nm LD激发下的红外荧光光谱的实验测量,系统研究了Nd3+:SrMoO4晶体的自受激拉曼光谱性质.分析指认了拉曼散射光谱中各拉曼峰所对应的晶格振动模式,得出了其SRS活性最强的声子频率约为898 cm-1,对应于(MoO2-4)离子团的完全对称光学伸缩振动Ag模;通过J-O理论对晶体的吸收谱进行了全面的光谱参数计算,得出4F3/2→4I11/2跃迁的积分发射截面达0.57×10-18 cm2,自发辐射概率为141.06 s-1;同时,实验测得该跃迁的荧光发射寿命约为0.2 ms.最后,结合808 nm LD激发下的红外波段荧光光谱,论证了SrMoO4晶体中Nd3+离子1068 nm发射通过拉曼频移获得1180 nm一级斯托克斯激光发射的可能性,为Nd3+:SrMoO4晶体的自受激拉曼激光器研究提供了理论依据.
关键词:
3+离子')" href="#">d3+离子
4 晶体')" href="#">SrMoO4 晶体
自受激拉曼散射 相似文献
7.
通过固相反应法制备了Er3+/Yb3+共掺杂ZrO2-Al2O3粉末的样品,并对样品在980nm激光激发下的上转换发光特性进行了研究.从发射光谱可以发现,在可见光范围内有3个强的发光带,一个位于654nm附近的红光带和两个分别位于545nm、525nm附近的绿光带,分别对应于Er3+离子的以下辐射跃迁:4F9/2→4I15/2、4S3/2→4I15/2、 2H11/2→4I15/2.其中又以Er3+离子的4F9/2→4I15/2跃迁产生的红色荧光辐射最强.对其上转换发光机制进行了分析,发现这三个发光过程都是双光子过程.对样品粉末进行了XRD检测,发现ZrO2主要以立方相为主,并且计算得到了这种立方结构的晶格常数.Al2O3固溶于ZrO2中,Al3+嵌入ZrO2后产生氧空位,导致ZrO2晶体的对称性降低,这种结构变化更有利于提高上转换效率,即上转换发光强度增强.
关键词:
3+/Yb3+')" href="#">Er3+/Yb3+
上转换
2-Al2O3')" href="#">ZrO2-Al2O3
荧光
稀土 相似文献
8.
9.
Seven absorption group-bands (1D2, 1G4, 3F2, 3F3, 3H4, 3H5, 3F4) of Tm3+ in YVO4 single crystals have been observed in the orientation absorption spectra recorded in the spectral range from 200 to 4000 nm at 300K. The integrated absorption cross section for each group-band was accurately evaluated. On the assumption that the anisotropy of this uni-axial crystal is small, the Judd-Ofelt theory was extended for the calculation of 4f-4f transition intensities of Tm3+ in YVO4. Two sets of phenomenological intensity parameters were derived from a least-squares-fit procedure. For c-axis cut sample we have Ω2=10.18 (10-20cm2), Ω4=1.96 (10-20cm2), Ω6=0.75 (10-20cm2).For a-axis cut sample we have Ω2=8.20 (10-20cm2), Ω4=2.47 (10-20cm2), Ω6=0.91 (10-20cm2). The anisotropy of the optical absorption intensities of Tm3+:YVO4 was theoretically analyzed in detail. 相似文献
10.
Synthesis and characterization of Ca2Sn1-xCexO4 with blue luminescence originating from Ce^4+ charge transfer transition 下载免费PDF全文
Ce^4+-doped Ca2SnO4 with a one-dimensional structure, which emits bright blue light, is prepared by using a solid-state reaction method. The x-ray diffraction results show that the Ce^4+ ions doped in Ca2SnO4 occupy the Sn^4+ sites. The excitation and emission spectra of Ca2Sn1-xCexO4 appear to have broad bands with peaks at - 268nm and -442nm, respectively. A long excited-state lifetime (-83μs) for the emission from Ca2Sn1-xCexO4 suggests that the luminescence originates from a ligand-to-metal Ce^4+ charge transfer (CT). The luminescent properties of Ca2Snl_xCexO4 have been compared with those of Sr2CeO4, which is the only material reported so far to show Ce^4+ CT luminescence. More interestingly, it is observed that the emission intensity of Ca2Sn1-xCexO4 with a small doping concentration (x - 0.03) is comparable to that of Sr2CeO4 in which the concentration of active centre is 100%. 相似文献
11.
基于完全对角化方法,研究了4B1(3d3)态 离子在四角对称晶场中的磁相互作用,分析了自旋哈密顿参量(b02, g∥, g⊥ , Δg)的微观起源.结果表明 :在被考虑的大部分晶场区域,人们通常考虑的SO(spin-orbit)磁相互作用的贡献最为重要 ;然而,对于零场分裂参量b02而言,来自其他机理(包 括SS(spin-orbit),SOO(sp in-other-orbit),SO-SS-SOO)的贡献在大部分晶场区域超过了20%;在部分晶场区域,其 他机理的贡献甚至超过SO机理的贡献.详细地分析了Macfarlane 零场分裂参量b02 近似三阶微扰理论的收敛性,结果表明:该理论在大部分晶场区域收敛性较差.讨论了3d3 态离子第一激发态2Eg分裂的微观起源.并利用 群论方法解 释了在C4v和C3v对称晶场中2Eg< /sub>态分裂的不同机理.
关键词:
4B1(3d3)态离子')" href="#">4B1(3d3)态离子
磁相互作用
自旋哈密 顿参量
完全对角化方法(CDM)
微扰理论方法(PTM) 相似文献
12.
13.
Theoretical calculation of of B-like ions: photoionization cross sections N^2+, O^3+ and F^4+ 下载免费PDF全文
There can be found some notable discrepancies with regard to the resonance structures when R-matrix calculations from the Opacity Project and other sources are compared with recent absolute experimental measurements of Bizau et al [Astron.Astrophts.439 387(2005)] for B-like ions N2+,O3+ and F4+.We performed close-coupling calculations based on the R-matrix formalism for the photoionizations of ions mentioned above both for the ground states and first excited states in the near threshold regions.The present results are compared with experimental ones given by Bizau et al and earlier theoretical ones.Excellent agreement is obtained between our theoretical results and the experimental photoionization cross sections.The present calculations show a significant improvement over the previous theoretical results. 相似文献
14.
A theoretical model to simulate an end-pumped CW Nd^3+:GdVO4 laser at 1063 nm is presented. Its essence is to use the propagation equations to demonstrate the spatial evolutions of the pump and the laser powers in the cavity, hence it is applicable to both low and high gain lasers. The simulation results obtained by this model are in good agreement with the experimental observations reported in the literature for a Ti:sapphlre-pumped Nd^3+:GdVO4 laser. Moreover, some parameters, such as the reflectivity of output coupler, the spot size of laser beam and the crystal length, are discussed with a view to optimizing the laser performance. 相似文献
15.
本文应用坩埚下降法技术在全密封铂金坩埚条件下生长了不同Pr3+离子掺杂浓度的高质量LiLuF4单晶. 测定了单晶体从420 nm至500 nm的激发光谱. 在446 nm光激发下,观察到单晶体480 nm(3P0→3H4)蓝色发射带、522 nm(3P1→3H5)绿色发射及605 nm(1D2→3H4)的红色发射,其对应的平均寿命分别为38.5、37.3和36.8 μs. 其荧光寿命明显大于Pr3+掺杂的氧化物单晶. 同时研究了激发波长和掺杂浓度对发射强度以及色度坐标的影响. 获得最佳的Pr3+浓度为∽0.5 mol%,并分析了环境温度从298 K 到443 K变化对荧光强度的影响. 结果表明随着温度的增加,荧光强度逐步变弱,其中3P0→3H4(480 nm)能级跃迁受温度影响最大,其次是3P1→3H5和1D2→3H4. 相似文献
16.
17.
采用高温固相法获得了一种只具有 微弱余辉的新型电子俘获型光存储材料Sr2SnO4:Tb3 +, Li +. 发光性能研究结果表明: 该材料对980 nm的红外激光具有很好的上转换光激励信息读出响应, 同时292 nm紫外光为其最佳信息写入光源. 光存储性能研究结果表明: 该材料的浅陷阱较少, 因此其余辉发光很弱, 不到500 s; 另一方面, 该材料中存在大量的深蓄能陷阱. 因此, Sr2SnO4: Tb3 +, Li+是一种具有较好实际应用价值的新型电子俘获型光存储材料. 此外, 还讨论了Sr2SnO4: Tb3 +, Li+的光存储发光机理. 相似文献
18.
Investigations of the electron paramagnetic resonance parameters and the tetragonal local structure for (VCl6)4- coordination complex in MCl:V2+ (M=Na, K, Rb) systems 下载免费PDF全文
By simulating the electron paramagnetic resonance (EPR) and optical spectra on the basis of the 120×120 complete energy matrix, this paper determines the local lattice structure parameters R1 and R2 for MCl:V2+ (M=Na, K, Rb) systems at 77 K, 195 K and RT (room temperature 295 K or 302 K), respectively. The theoretical results indicate that there exists a compressed distortion in MCl:V2+ systems. Meanwhile, it finds that the structure parameters R1, R2 and |△R| (= R1-R2) increase with the rising temperature. Subsequently, from the analysis it concludes that the relation of EPR parameter D vs.△R is approximately linear. Finally, the effects of orbital reduction factor k on the g factors for the three systems have been discussed. 相似文献
19.
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. 相似文献