Low-temperature specific heat of erbium pnictides

By studying the specific heat of samples of different quality it is shown that the character of the specific-heat anomaly depends sensitively on the quality of the crystals. Our result on Er monopnictides indicated that the transition is of first order. It seems unlikely that successive structural (quadrupole) and magnetic transitions occur in these compounds.     

Reinvestigation of the high spin states in ^（161）Er and enhanced E1 transitions in the N=93 isotones

High-spin states in ¹⁶¹Er have been studied experimentally using the ¹⁵⁰Nd(¹⁶O, 5n) reaction at a beam energy of 86 MeV. The relatively enhanced E1 transitions between the 5/2⁺[642] and 3/2^-[521] bands are observed in ¹⁶¹Er, and the B(E1) values are extracted experimentally. The systematics of the R(E1) values in the N=93 isotones are presented. It is found that the strength of the E1 transitions obviously exhibits angular momentum dependence, and the occurrence of the relatively enhanced E1 transitions could be attributed to octupole softness.     

Investigation of the magnetic properties of the Gd1−xErx alloy system in the x < 0.62 composition range

The magnetic properties of the Gd---Er system (with erbium concentrations ranging from 0 to 62 at%) were investigated at temperatures between 4.2 and 350 K under external magnetic fields up to 1 T. The results show that, similar to other rare-earth systems, simple ferromagnetism prevails for concentrations with a de Gennes factor G higher than about 11.5 (≈ 30 at % Er) while complex magnetic structures are present for higher Er concentrations (G ≤ 11.5. The magnetic transition temperature decreases with increasing Er content, showing good agreement with phenomenological expectations. In the paramagnetic region, the Curie constant of the alloy corresponds to the linear combination of the constituent elements' contribution, thus proving that both Gd and Er maintain their individual magnetic moments. From magnetization data below the transition, the change in magnetic entropy for a 1 T field was calculated and this showed distinct differences between ferromagnetic-paramagnetic transitions and antiferromagnetic transitions. The Landau theory of second-order phase transitions can be well applied for evaluating the thermodynamic transition temperature and the specific heat anomaly in the ferromagnetic alloys but it fails for the more complex structures if the applied field is not far higher than the critical field. The magnetic entropy change displays well defined peaks at the transition temperature for both ferromagnetic and antiferromagnetic alloys. There is an indication that the spin-reorientation transition occurring in alloys with higher Er concentrations is also coupled with significant magnetic entropy changes.     

Probability of statistical L-H transition in tokamaks

A statistical model for the bifurcation of the radial electric field Er is analyzed in view of describing L-H transitions of tokamak plasmas. Noise in microfluctuations is shown to lead to random changes of Er if a deterministic approach allows for more than one solution. The probability density function for and the ensemble average of Er are obtained. The L-to-H and the H-to-L transition probabilities are calculated, and the effective phase limit is derived. Because of the suppression of turbulence by shear in Er, the limit deviates from Maxwell's rule.     

Multipolarity of the continuum γ-rays in 152Dy and 160Er via linear polarisation measurements

The multipolarity of the continuum transitions in ¹⁵²Dy and ¹⁶⁰Er has been deduced from γ-ray linear polarisation and angular distribution measurements. The yrast part for ¹⁶⁰Er agrees with the predicted stretched E2 cascade. The statistical parts for both ¹⁵²Dy and ¹⁶⁰Er consist of a mixture of dipolar stretched and non-stretched transitions, predominantly of electrical character. Below 1.5 MeV, the data of ¹⁵²Dy exhibit a different structure, and reveal a stretched M1 component in the low-energy region.     

145Er的β延发质子衰变性质研究

通过92Mo(58Ni, 2p3n)熔合蒸发反应生成了非常缺中子核145Er。利用氦喷嘴带传输系统把研究目标核传输到低本底测量站, 进行了质子 γ符合测量, 得到了不受同量异位素干扰的145Er的β延发质子谱。经过仔细分析与延发质子符合的γ谱, 发现了145Er的11/2-同核异能态具有β延发质子衰变性质。经拟合退激144Dy不同激发态γ跃迁的衰变曲线, 得出145Er的1/2+基态和11/2-同核异能态的半衰期分别为(1.6±0.6)和(0.6±0.1) s。最后, 简单介绍了中重质量区缺中子新核素的合成及衰变研究计划。The neutron deficient isotope 145Er was produced via the fusion evaporation reaction 92Mo(58Ni, 2p3n). The reaction products were transported to a low background counting area using a He jet tape transport system, and proton γ coincidence measurements were carried out. Based on the analysis of γ transitions in coincidence with β delayed protons, the β delayed proton decay of an νh11/2 isomer in 145Er was proposed. By fitting the decay curves of the γ transitions depopulating the low lying states in 144Dy, the half lives of the ground state and the νh11/2 isomeric state in 145Er were deduced to be (1.6±0.6) and (0.6±0.1) s, respectively. An experimental plan to synthesize new β delayed proton precursors in the medium heavy mass region has been presented.     

Na5Er(WO4)4晶体的光谱参数

Na5Er(WO4)4是化学计量的基质发光晶体,含有很高浓度的Er,它的发光却没有明显的浓度猝灭.与Na5Er(WO4)4结构相同的Na5Nd(WO4)4单晶是良好的激光材料,已获得激光输出.而Er3+在YAlO3,Y3Al5O12和CaF2中也实现了激光输出[1],在ErP5O14[1],Y3Al5O12:Er3+[2]和掺Er3+磷酸盐玻璃[3]的光学参数和某些谱线出激光的可能性已有研究.     

970nm抽运下Er3+/Yb3+/Tm3+共掺碲酸盐玻璃的发光特性

研究了Er3+/Yb3+共掺、Tm3+/Yb3+共掺、Er3+/Yb3+/Tm3+共掺碲酸盐玻璃在970nm抽运下的荧光光谱和上转换光谱性质，测试了Er3+离子的4I11/2和4I13/2能级荧光寿命变化情况.结果发现Er3+/Yb3+/Tm3+共掺碲酸盐玻璃的常规荧光谱线在1450—1700nm区域明显加宽，并在1630nm有一荧光峰，可能是Tm3+：1G4→3F2跃迁产生.上转换发光研究表明，由于碲酸盐玻璃声子能量低的缘故，三种共掺系统下都存在上转换发光现象.在Er3+/Yb3+/Tm3+共掺中，上转 关键词： Er3+/Yb3+/ Tm3+共掺 碲酸盐玻璃 荧光 上转换光谱     

Lifetimes of unresolved transitions from very high spin states in nuclei nearN=82

Average lifetimes of unresolved transitions deexciting very high spin states populated in²⁸Si(^{136, 129}Xe,xn)^164? x, 157?xEr reactions have been determined by a Doppler shift attenuation method. We find that the yrast bump region between 1.0 and 1.6 MeV contains a majority of strongly collectiveE2 transitions with very short lifetimes (a few tens of fsec) in the well deformed nuclei around¹⁵⁹Er and, with less certainty, almost comparably short lifetimes in the more spherical nuclei around¹⁵²Er. In the high energy region of 2.0–3.2 MeV we observe transitions which depopulate longer lived states in the nuclei nearN=82 than in the well deformed systems.     

Kinetics of CO Molecules Taking into Account Resonant VE Exchanges in a Nonequilibrium Nozzle Flow

The kinetics of CO molecules with excited electronic levels for a nonequilibrium flow in nozzles is studied. Three electronic energy levels are taken into account; the VV exchanges of the vibrational energy within each electronic energy level, VT transitions from the vibrational energy to the translational energy, and VE exchanges between the vibrational energy and the electronic terms occur in the system. The system of equations of vibrational level kinetics and gasdynamics, which is written in the zeroth approximation of the Chapman–Enskog method, is solved numerically. Special attention is paid to estimating the effect of the VE exchanges of the vibrational energy on the formation of nonequilibrium populations of the vibrational levels. It is shown that resonant VE transitions considerably affect the relaxation process and noticeably change the population of the upper vibrational levels even in the absence of recombination and dissociation processes; VE exchanges also affect the time dependence of the vibrational temperature.     

Er3+单掺,Er3+/Yb3+共掺杂氟化物中红绿上转换荧光机理实验探索

制备了稀土离子Er^3＋单掺,Er^3＋-Yb^3＋共掺杂氟化物样品。在980nm波长激光激发下,室温时观察到了清晰可见的红（650nm）绿（545nm）上转换荧光,它们分别对应^4S3/2,^2H11/2-^4I15/2和^4F9／2-^4I15/2的发射。同时发现红绿上转换荧光的比值随Er^3＋的浓度增加而减少（对共掺而言）。上换荧光强度与激发光强度的关系表明红绿上转换荧光都是双光子上转换过程,在此基础上,根据能量匹配的原理,讨论了红绿上转换荧光的可能实现机制。     

Mathematical Simulation of Low-Frequency Mechanical Action on Bimolecular Reaction Kinetics in a Structured Liquid

A mathematical model of the physicochemical processes that occur under low-frequency mechanical action on bimolecular reaction kinetics with consideration for the association of reagents is presented. As a result of the mathematical simulation, special features of the kinetics and stability of the reaction modes were established. It was shown that, in a structured liquid, a formally simple reaction occurs as a complex process with the appearance of bistability regimes, the formation of a temporal dissipative structure, and the complex structure of intermediate concentration oscillations. The possibility of controlling transitions from stable to unstable reaction conditions and vice versa under changes in the external action amplitude was demonstrated.     

Photoluminescence spectra of intracenter 4f transitions of rare-earth metal dopants in crystalline ZnO films

The influence of annealing in the medium of an ionized nitrogen, additionally introduced impurities, and regimes of post-growth annealing on photoluminescence spectra of intracenter 4f transitions of rare-earth metal dopants (Ce, Eu, Sm, Er, Tm, Yb) in crystalline ZnO films has been investigated. The films have been prepared using molecular-beam epitaxial growth and magnetron sputtering. According to the X-ray diffraction analysis, the films have a single-crystal structure. It has been shown that the annealing in the medium of an ionized nitrogen, regardless of the method used for producing the ZnO films, leads to significant changes in the photoluminescence spectrum, i.e., to a decrease in the emission intensity and a shift in the position of the emission maximum toward the long-wavelength range of the spectrum. The nitrogen concentration has been determined by the nuclear reaction method. It has been revealed that the spectra contain intense emission lines due to the intracenter 4f transitions of rare-earth elements (Sm, Er, Tm, Yb) in the crystalline ZnO films prepared by magnetron sputtering, and the intensity of the emission lines increases upon introduction of codopants, namely, Ce and Er.     

A method for solving phase transition equations

The kinetics of phase transitions is calculated on the assumption of mechanical and temperature equilibrium between mixture components. The simulation of kinetics is based on solving relaxation-type kinetic equations. The deviator components of the constituents of a mixture of phases are assumed to be equal. When a material is deformed, several phase transitions can occur simultaneously. The determination of the thermodynamic parameters of mixture components is based on solving linearized equations for component pressure and temperature increments at known specific volume and mixture energy increments. We suggest an effective algorithm for solving these equations. The algorithm is based on an explicit Lagrangian difference scheme and takes into account pressure and temperature discrepancies. The algorithm is implemented in the SPRUT two-dimensional program. We present the results of calculations for one-and two-dimensional problems with and without taking into account the α-? transition in iron.     

LaOBr:Er3+,Tm3+红外跃迁的研究

对在基质LaOBr中分别加入Er3+和Tm3+稀土离子时的红外光谱强度随Er3+和Tm3+离子浓度的变化规律进行了研究.通过对在基质LaOBr中同时加入Er3+和Tm3+稀土离子对它们的发光强度随着浓度的变化呈现不同规律的研究,证实了发生于Er3+和Tm3+稀土离子之间的能量转移是影响Er3+和Tm3+红外发光的重要因素.并且,这种能量转移过程是以共振传递的方式进行的.另外,通过对Er3+的4S3/2能级寿命的测量,给出这种能量转移的直接证据.     

Er3+/Yb3+共掺杂氧氟硅酸盐玻璃的上转换发光

研究了Er^3 ／Yb^3 共掺氧氟硅酸盐玻璃的吸收光谱、上转换光谱和拉曼光谱。分析了氧氟硅酸盐玻璃中Yb”敏化Er^3 的上转换发光机理。结果表明：通过975nm的激光二极管激发,在室温下同时观察到蓝光(408nm)、绿光(529nm和545nm)和红光(667nm),分别是由于Er^3 离子。H9/2→^4I15/2,H11/2→^4I15/2,H3/2→^4I15/2和H9/2→^4I15/2跃迁。随Yb2O3浓度的增加。Yb^3 对Er^3 的能量转移增强,因此蓝光、绿光和红光的发光强度都增强,强烈的绿光和红光激发是由于双光子吸收过程,而微弱的蓝光是由于三光子吸收过程。拉曼光谱发现,对Er^3 离子在氧氟硅酸盐玻璃中的上转换发光。玻璃结构中的PbF2起到重要作用。     

Er3+掺杂重金属氧氟硅酸盐玻璃的上转换发光研究

研究了Er3+掺杂重金属氧氟硅酸盐玻璃的吸收光谱、上转换光谱和拉曼光谱，分析了重金属氧氟硅酸盐玻璃中Er3+的上转换发光机理. 结果表明：通过975nm的激光二极管激发，在室温下同时观察到蓝光(411nmj)、绿光(525和543nm)和红光(655nm)，分别是由于Er3+离子2H9/2→4I15/2, 2H11/2→4I15/2, 4S3/2→4I15/2, 和4F9/2→4I15/2跃迁. 随Er2O3浓度的增加，蓝光、绿光和红光的发光强度都增强，上转换发光机理主要涉及能量转移和激发态吸收，强烈的绿 关键词： Er3+离子 重金属氧氟硅酸盐玻璃 上转换光谱 发光机理     

Nanosecond dynamics of the near-infrared photoluminescence of Er-doped SiO2 sensitized with Si nanocrystals

We report on an observation of a fast 1.5 microm photoluminescence band from Er3+ ions embedded in an SiO2 matrix doped with Si nanocrystals, which appears and decays within the first microsecond after the laser excitation pulse. We argue that the fast excitation and quenching are facilitated by Auger processes related to transitions of confined electrons or holes between the space-quantized levels of Si nanocrystals dispersed in SiO2. We show that a great part--about 50%--of all Er dopants is involved in these fast processes and contributes to the submicrosecond emission.     

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。     

Charge-density-wave transitions in the local-moment magnet Er5Ir4Si10

We report the observation of a new type of charge-density wave (CDW) in the large magnetic-moment rare-earth intermetallic compound, Er5Ir4Si10, which then orders magnetically at low temperatures. Single crystal x-ray diffraction shows the development of a 1D incommensurate CDW at 155 K, which then locks into a purely commensurate state below 55 K. The well-localized Er3+ moments are antiferromagnetically ordered below 2.8 K. We observe very sharp anomalies in the specific heat at 145 and 2.8 K, signifying the bulk nature of these transitions. Our data suggest the coexistence of strongly coupled CDW with local-moment antiferromagnetism in Er5Ir4Si10.