Luminescence of [Be] centre in MgO:Be

Doping of MgO single crystals with Be results in the formation of numerous Be-containing paramagnetic centres, easily detectable by EPR, and creates an intensive luminescence band at 6.2 eV, observable at T<200 K, and gives rise to new thermoluminescence peaks at 147 and 190 K. A paramagnetic centre with a rhombic symmetry that decays at 160 K was identified as a [Be]⁺ (i.e. O⁻–Be²⁺) centre—a hole trapped by O²⁻ lattice ion near a Be²⁺ perturbing defect. The luminescence excitation and isochronal annealing studies led to the conclusion that the 6.2 eV luminescence arises at the radiative decay of electron excitations near Be²⁺. These excitations can be created at the recombination of electrons with the holes localised in the [Be]⁺ centres, at the recombination of holes with the electrons trapped in the Be¹⁺ centre or at a direct excitation of oxygen near the Be²⁺ ion.     

弱时间简谐电场中类氢原子的变分微扰计算Ⅱ:激发态(21±1)和(32±2)

本文是文献[4]的续篇,采用基于Schrödinger方程流体动力学相似模型的变分微扰法计算了弱时间简谐电场中类氢原了H、He⁺、Li⁺²、Be⁺³、B⁺⁴激发态(21±1)和(32±2)的扰动波函数以及极化率与第一共振频率,讨论了电子云随时间的变化。结果表明,极化率与第一共振频率的计算值与精确值值符合得很好。结果再次表明,在应用变分微扰法计算极化率时,振幅微扰项∈与幅角项S是同等重要的。本文及文献[4]的工作部分地完成了Askar等人在文献[3]中宣布将要进行的工作。     

采用B样条有限基集获得等电子系列基态关联能

报导了基于组态相互作用模型对几种双电子原子(离子)系统基态电子关联能的计算方法研究,方法上属于变分法应用的范畴,技巧上采用B样条处理径向基,同时又用Goldman[3]提出的"混合L"法处理角向基,给出He,H^-,Li⁺,Be⁺⁺,B⁺⁺⁺等五种原子(离子)系统的有关计算结果,还与其它理论方法的相应结果作了对比,显示出良好的计算精度和效率     

Electron-impact ionization cross section calculations for lithium-like ions

The electron-impact ionization of lithium-like ions C³⁺,N⁴⁺,O⁵⁺,Ne⁷⁺,and Fe2³⁺is studied using a combination of two-potential distorted-wave and R-matrix methods with a relativistic correction.Total cross sections are computed for incident energies from 1 to 10 times of ionization energy and better agreements with the experimental results are obtained in comparison with the theoretical data available.It is found that the indirect ionization processes become significant for the incident energy larger than about four times of the ionization energy.Contributions from the exchange effects along the isoelectronic sequence are also discussed and found to be important.The present method can be used to obtain systematic ionization cross sections for highly charged ions across a wide incident energy range.     

Calculations of Local Distortions Around the Orthorhombic Gd3+ : M+: CaF2 Complexes

A reliable lattice relaxation model is developed in detail for calculating the ionic positions of Gd³⁺ at orthorhombic sites in CaF₂ with a nearby charge-compensating M⁺ ion (M=Li,Na, KJ Rb and Cs). In this model, all the ionic displacements induced by the Gd³⁺ and M⁺ impurity ions are treated using the discrete atomistic basis. In comparison with some experimental data on the ionic shifts in the Gd³⁺: M⁺: CaF₂ complex, our calculated results are found to be much better than the previous calculations based on the semi-discrete approach with a dielectric continuurn approximation.     

多孔性氟化物助熔剂制备Eu2+:(Sr,Ca) AlSiN3红色荧光粉

H-PAF （Micro-porous aluminum fluoride）是一种比表面积为20~200 m²/g的多孔性氟化物,具有熔点低、活性高等特性。在Eu²⁺：（Sr,Ca） AlSiN₃烧成工艺中作为助熔剂使用,与传统的氟化物、硼酸等助熔剂相比,可以有效增加Eu²⁺：（Sr,Ca） AlSiN₃荧光粉在合成过程中总的反应活性,降低反应温度50℃以上,并改善荧光粉的发光性能。本文以H-PAF多孔性氟化物为助熔剂,合成了Eu²⁺：（Sr,Ca） AlSiN₃荧光粉,合成温度从1 800℃降低到1 750℃,而且XRD衍射峰更尖锐,说明H-PAF的添加使晶体结晶性更好。测试了Eu²⁺：（Sr,Ca） AlSiN₃荧光粉搭配Ga-YAG绿色荧光粉制成器件后的光效。发现添加PAF后,Eu²⁺：（Sr,Ca） AlSiN₃荧光粉用粉量降低约5%,器件光通量提高2%以上。     

A study of the Ti(He, t) and Ni(He, t) reactions to isobaric analogue states

The (³He, t) reaction populating 0⁺ and 2⁺ states in ^{58, 60}Cu and ^{46, 48}V which are isobaric analogue states (IAS) of the 0⁺ ground states and 2⁺ first excited states in ^{58, 60}Ni and ^{46, 48}Ti have been studied at an incident ³He energy of 24.6 MeV. Triton spectra were measured for the targets ^46,48Ti, ^natNi and ⁵⁸Ni and angular distributions for the 0⁺ and 2⁺ IAS of ^{46, 48}Ti and ^{58, 60}Ni determined. The data were obtained using a magnetic spectrometer and position-sensitive detectors. The results have been analysed using DWBA theory. The 0⁺ → 0⁺ transitions to analogue states are described quite well using a microscopic form factor derived from a nucleon-nucleon interaction. However, with a Gaussian form, the m.s. radius of this interaction is only limited to the region 0–9 fm². Comparisons with data at other incident energies indicate that the strength of the effective interaction is strongly energy dependent. The Coulomb energies and (³He, t) angular distributions of the states assigned as the 2⁺ analogues in ⁴⁸V and ^58,60Cu are not described well by the models investigated. The ⁴⁶V 2⁺ IAS angular distribution is reproduced by a microscopic calculation, however. The ratios of the 0⁺ → 2⁺ IAS to the 0⁺ → 0⁺ IAS transitions are used to deduce a quadrupole deformation for the valence neutrons. The difference in the quadrupole deformations of the matter and proton distributions, as determined by other means, is found to be correlated with those of the valence neutrons. Several transitions to non-analogue states are also investigated.     

纳米壳聚糖复合材料的制备与性能研究

为了提高壳聚糖的水溶性及其止血方面的性能,将壳聚糖(CS)纳米化,并引入具有抗菌作用的Ag~+离子和凝血辅助作用的Ca~(2+)离子,制备出纳米壳聚糖金属离子复合止血材料。首先,采用离子交换法制备纳米壳聚糖(nmCS),再分别加入AgNO_3和饱和CaCl2溶液,制得nmCS-Ag、nmCS-Ca、nmCS-Ag-Ca复合材料。然后,采用FTIR、XRD、SEM等手段对复合材料的结构进行表征。最后,对复合物的凝血、止血性能进行了测试。实验结果表明:改性后的壳聚糖IR图谱在1647cm-1和1560cm-1处出现了纳米壳聚糖钠盐的特征吸收峰;复合了金属离子的纳米壳聚糖在XRD图谱中表现出了Ag~+、Ca~(2+)的晶型特征;扫描电镜显示nmCS-Ag中Ag~+有部分析出而nmCS-Ca的复合效果较好;nmCS-Ag-Ca的凝血、止血效果要优于nmCS-Ag和nmCS-Ca,同时nmCS-Ag和nmCS-Ca的凝血、止血效果要优于nmCS。测试结果表明,成功制备了纳米壳聚糖金属离子复合止血材料。     

Numerical analysis of motional mode coupling of sympathetically cooled two-ion crystals

A two-ion pair in a linear Paul trap is extensively used in the research of the simplest quantum-logic system; however,there are few quantitative and comprehensive studies on the motional mode coupling of two-ion systems yet. This study proposes a method to investigate the motional mode coupling of sympathetically cooled two-ion crystals by quantifying three-dimensional(3 D) secular spectra of trapped ions using molecular dynamics simulations. The 3 D resonance peaks of the ~(40)Ca~+ – ~(27)Al~+ pair obtained by using this method were in good agreement with the 3 D in-and out-of-phase modes predicted by the mode coupling theory for two ions in equilibrium and the frequency matching errors were lower than 2%.The obtained and predicted amplitudes of these modes were also qualitatively similar. It was observed that the strength of the sympathetic interaction of the ~(40)Ca~+ – ~(27)Al~+ pair was primarily determined by its axial in-phase coupling. In addition,the frequencies and amplitudes of the ion pair's resonance modes(in all dimensions) were sensitive to the relative masses of the ion pair, and a decrease in the mass mismatch enhanced the sympathetic cooling rates. The sympathetic interactions of the ~(40)Ca~+ – ~(27)Al~+ pair were slightly weaker than those of the ~(24)Mg~+– ~(27)Al~+ pair, but significantly stronger than those of ~9Be~+ – ~(27)Al~+ . However, the Doppler cooling limit temperature of ~(40)Ca~+ is comparable to that of ~9Be~+ but lower than approximately half of that of ~(24)Mg~+. Furthermore, laser cooling systems for ~(40)Ca~+ are more reliable than those for ~(24)Mg~+and ~9Be~+ . Therefore, ~(40)Ca~+ is probably the best laser-cooled ion for sympathetic cooling and quantum-logic operations of ~(27)Al~+ and has particularly more notable comprehensive advantages in the development of high reliability, compact, and transportable ~(27)Al~+ optical clocks. This methodology may be extended to multi-ion systems, and it will greatly aid efforts to control the dynamic behaviors of sympathetic cooling as well as the development of low-heating-rate quantum logic clocks.     

基于紫外或蓝光LED激发的Eu3+和Bi3+共掺杂LaMgB5O10红色荧光粉

采用固相法合成了Eu3+和Bi3共掺杂的LaMgB5O10红色荧光粉,在紫外或蓝光激发下,样品的红光强度随着Bi2O3的增加而增强.利用X射线衍射对样品的结构进行了分析,结果表明,掺入Bi2O3后,样品的结晶度更好.根据Judd-Ofelt理论计算,得到样品的内量子效率不随掺杂剂的改变而变化,约为43％.在394nm激...     

Sm3+掺杂对CaMoO4:Eu3+红色荧光粉结构和发光性质的影响

采用共沉淀法制备了CaMoO4:Eu3,Sm3+纳米荧光粉材料.系统研究了Sm3+离子的引入对CaMoO4:Eu3+材料的结构和发光性质的影响.结果表明:纳米材料的尺寸随着Sm3+离子掺杂浓度的增加而变小.Sm3+的引入,可实现Sm3+和Eu3+之间的能量传递,使Eu3+在近紫外405 nm处的激发增强,进而使Eu3+...     

AN INVESTIGATION FOR THE Cd2+-VACANCIES IN RbCdF3 and CsCdF3 CRYSTALS DOPED WITH Fe3+ IMPURITIES

This paper presents high-order perturbation calculations for the zero-field splitting parameters D, F, and a of Fe³⁺-V_Cd pairs in RbCdF₃ and CsCdF₃ crystals doped with Fe³⁺ impurities. In comparison with experimental data, the present results are better than those obtained in previous work by using the phenomenological su-perposition model of spin-Hamiltonian. Moreover, the crystal fields arising from the Cd²⁺-vacancy and their induced crystal lattice distortion are analysed and calculated. It is found that the contribution from the Cd²⁺-vacancies cannot be ignored. Mena-while, we obtain that a ligand F^- along the [001]-axis moves towards the central Fe³⁺ ion by Δ= 0.0020nm in RbCdF₃ and 0.0028nm in CsCdF₃. These results are quite different from Δ = 0.0104nm and Δ = 0.0112nm, respectively, obtained in previous work by using the superposition model of spin-Hamiltonian and ignoring the effect of the vacancy.     

用23Na、14N NMR方法测定Na+、NH4+与18-冠-6在水溶液中的络合平衡常数

用与Popov等不同的多核NMR化学位移方法测定了水溶液中Na⁺及NH₄⁺与18-冠-6的络合平衡常数K分别为logK=0.72和logK=1.21。对实验方法、多核线宽等进行了讨论。     

Dependence of Auger depth resolution and surface texturing on primary ion species

The dependence of Auger depth resolution and surface texturing on primary ion species was systematically investigated for polycrystalline Al, Mo, Ag and Ta films deposited on Si wafers, using 3 keV Ne⁺, Ar⁺ and Xe⁺ ions as projectiles. The resolution was found to depend strongly on ion species; the higher the ion mass, the better the resolution. The resolution improvement attained with Xe⁺ ions was dramatic for Al, becoming less pronounced for higher mass targets. As revealed by high-resolution scanning electron microscopy, Xe⁺ sputtering led to less-developed topographical structures of sputtered areas, which allowed us to conclude that ion sputtering with heavier ions roughens the surface less, resulting in a marked improvement in resolution.     

Electroproduction of π from C leading to low-lying residual states in B

Energy distributions of π⁺ produced from ¹²C by electrons of total energy 195 MeV were measured at various angles. The results show large contributions from transitions leaving the residual nucleus in the ground (1⁺), first (2⁺) excited state and states at around 4.5 MeV. The angular distributions of ¹²C(γ, π⁺)¹²B leading to these residual states are deduced from the energy distributions by the unfolding method with the virtual photon theory. Theoretical results with the Helm model and the shell model are compared with the experimental results. Their relative shapes are in good agreement. A better agreement in the absolute value is found for the theoretical results which include the final-state interaction estimated with a pion optical potential. The surface production model shows better agreement with the experimental (γ, π⁺) cross sections than the volume production model.     

荧光粉MPO4：Eu3+,Bi3+/Tb3+ (M=La,Gd,Y) 的结构及发光性能研究

采用高温固相法合成了一系列MPO₄：Eu³⁺,Bi³⁺ （M=La,Gd,Y）及 MPO₄：Tb³⁺ （M=La,Gd,Y）荧光粉材料,用X射线衍射（XRD）仪对样品结构进行了表征。所合成的LaPO₄和GdPO₄属单斜晶系,而YPO₄属体心立方晶系。用Diamond软件对结构进行分析并绘出了晶胞结构。对样品发光性质的研究结果表明,虽然MPO₄（M=La,Gd,Y）均属于正磷酸盐,但由于晶格结构不同,其发光性质也不同。立方晶系的YPO₄更有利于掺入其中的稀土离子的发光,Bi³⁺离子的引入能够明显改善样品的发光性能。     

YAlO3晶体中pr3+的4f2能级

YAlO3∶pr3+是一种受到广泛关注的发光体系,本文根据文献中给出的YAlO3∶pr3+晶体中Pr3+的晶体场能级,从Nd3+离子的晶体场参数和Pr3+的准自由离子参数出发,采用f-shell计算软件包对pr3+的能级参数进行了研究,并对获得的参数进行了讨论.用拟合获得的参数计算了pr3+的4f2电子构型的所有能级.     

The luminescence properties of the ZnO@ZnWO4:Eu core–shell composites

The ZnO@ZnWO₄:Eu³⁺ core–shell composites were prepared by a two-step hydrothermal method and the photoluminescence properties of the composites were studied in contrast to the corresponding hexagonal ZnO and monoclinic ZnWO₄: Eu³⁺ nanocrystals prepared by the one-step hydrothermal method. The results demonstrate that in the nanocomposites the Eu³⁺ ions in the ZnWO₄ phase occupy two symmetry sites, one a well-crystalline inner site and one a disordered surface site; while in the ZnWO₄: Eu³⁺ nanocrystals, the local environments surrounding Eu³⁺ ions are relatively disordered for both the inner and the surface sites. This indicates that in the composites, the crystallinity of the ZnWO₄ becomes better, which have positive influence on the improvement of photoluminescence. The temperature stabilities for both the emissions of ZnO and Eu³⁺ ions are improved in contrast to the pure ZnO or ZnWO₄:Eu³⁺ nanocrystals.     

Comparison between MeV Ni and He ion-implanted planar optical waveguides in quartz

Optically polished crystalline quartz samples were implanted at room temperature by 2.6 MeV Ni⁺ ions with a dose of 9×10¹⁴ ions/cm² and 2.0 MeV He⁺ ions with a dose of 1.5×10¹⁶ ions/cm², respectively. A comparison of the MeV Ni⁺ ion-implanted planar waveguide formation was made with the MeV He⁺ ion-implanted one. The prism-coupling method was carried out to measure the dark modes in the quartz waveguides by using model 2010 prism coupler. Five modes were observed in the Ni⁺ implanted waveguide while 15 modes were found in the He⁺ ion-implanted one. Reflectivity calculation method was applied to fitting the refractive index profile. TRIM’98 (transport of ions in matter) code was used to simulate the damage profile in quartz by MeV Ni⁺ and He⁺ ions implantation, respectively. It is found that the refractive index profile in MeV Ni⁺ ions implanted waveguide is somewhat different in shape from that in MeV He⁺ ions implanted waveguide.     

Theoretical calculations of hyperfine splitting,Zeeman shifts,and isotope shifts of 27Al+ and logical ions in Al+ clocks

Based on the multiconfiguration Dirac-Hartree-Fock (MCDHF) method, similar models are employed to simultaneously calculate the first-order and second-order Zeeman coefficients as well as the hyperfine interaction constants of the related energy levels of ²⁷Al⁺ and its logical ions ⁹Be⁺ and ²⁵Mg⁺ in the ²⁷Al⁺ optical clock. With less than 0.34% deviations from experimental values in Zeeman coefficients of ²⁷Al⁺, these calculated parameters will be of great help for better evaluation of the systematic uncertainty. We also calculate the isotope shift parameters of the related energy levels, which could extend our knowledge and understanding of nuclear properties of these ions.