The fission barrier of actinide nuclei at very high angular momentum

The Strutinsky approach with a cranked, axially symmetric Saxon-Woods potential, is used to study the double-humped fission barrier of ²⁴⁰Pu at very high spins. The stabilizing role of the shell effects in the second minimum is demonstrated.     

Some comments on the use of phased angular momentum states in the theory of coherent spontaneous emission from large systems

We stress the importance of using phased atomic states when describing coherent spontaneous emission from large atomic systems. A sufficient criterion for the existence of a preferred direction of emission is deduced from dynamical arguments.     

高入射能量下的金属二次电子发射模型

基于高入射能量电子产生二次电子发射的物理过程, 分别对高入射能量电子产生的真二次电子和背散射电子的概率进行理论分析与建模. 利用Bethe能量损失模型和内二次电子逸出概率分布, 推导出高入射能量电子产生有效真二次电子发射的系数与入射能量的关系式; 根据高入射能量电子在材料内部被吸收的规律, 推导出高入射能量电子产生背散射电子的系数与入射能量之间的关系式. 结合两者得到高入射能量下金属的二次电子发射模型. 利用该模型计算得到典型金属材料Au, Ag, Cu, Al的二次电子发射系数, 理论计算结果与采用Casino软件模拟金属内部散射过程得到的数值模拟结果相符. 关键词： 二次电子发射 高入射能量 金属表面 散射过程     

Effect of entrance-channel asymmetry on the isospin dependence of nucleon emission in heavy ion collisions

Using the isospin- and momentum-dependent hadronic transport model IBUU04, we have in-vestigated the influence of the entrance-channel isospin asymmetry on the sensitivity of the pre-equilibrium neutron/proton ratio to symmetry energy in central heavy-ion collisions induced by high-energy radioactive beams. Our analysis and discussion are based on the dynamical simulations of the three isotopic reaction systems 132Sn+124Sn, 124Sn+112Sn and 112Sn+112Sn which are of the same total proton number but different isospin asymmetry. We find that the kinetic-energy distributions of the pre-equilibrium neutron/proton ratio are quite sensitive to the density-dependence of symmetry energy at incident beam energy E/A = 400 MeV,and the sensitivity increases as the isospin asymmetry of the reaction system increases.     

金属的高能二次电子发射系数与入射能量和能量幂次的关系

根据原电子射程表达式和金属的有效真二次电子发射系数表达式,推导出金属的高能有效真二次电子发射系数与入射能量、能量幂次的关系式;并根据金属的高能有效真二次电子发射系数与金属的高能二次电子发射系数的关系,推导出金属的高能二次电子发射系数与入射能量、能量幂次的关系式。用实验数据计算出高能原电子轰击在金或银上时原电子入射能量幂次n,采用实验数据证实高能二次电子发射系数与原电子入射能量和能量幂次三者的关系,对结果进行讨论并得出结论：当高能原电子轰击在同一块金属上时,高能二次电子发射系数与原电子入射能量的n-1次幂之积近似为一常数。     

原子薛定谔猫态中角动量的压缩及其时间演化

在低Q值腔内，原子相干态在一些特定时刻可以演化为原子薛定谔猫态.讨论了在这种原子薛定谔猫态中原子角动量的涨落和高阶涨落.根据不确定性原理，进一步研究了原子角动量的压缩和高阶压缩性质及其演化.研究表明，原子薛定谔猫态可以被压缩到二阶和六阶，但不能被压缩到四阶.当原子薛定谔猫态中被叠加的原子相干态数为无限多项时，其压缩特性与原子相干态相同. 关键词： 原子相干态 薛定谔猫态 角动量压缩 Bloch态     

金属的高能二次电子发射系数与入射能量和能量幂次的关系

 根据原电子射程表达式和金属的有效真二次电子发射系数表达式,推导出金属的高能有效真二次电子发射系数与入射能量、能量幂次的关系式;并根据金属的高能有效真二次电子发射系数与金属的高能二次电子发射系数的关系,推导出金属的高能二次电子发射系数与入射能量、能量幂次的关系式。用实验数据计算出高能原电子轰击在金或银上时原电子入射能量幂次n,采用实验数据证实高能二次电子发射系数与原电子入射能量和能量幂次三者的关系,对结果进行讨论并得出结论：当高能原电子轰击在同一块金属上时,高能二次电子发射系数与原电子入射能量的n-1次幂之积近似为一常数。     

高功率激光片状放大器中自发辐射放大研究

 采用理论模拟和实验研究相结合的方法，研究了高功率激光片状放大器中的自发辐射放大(ASE)效应。建立了一套较完整的包含空间和时间的3维ASE模型，分析了不同电压、不同储能分布和不同泵浦时刻、不同增益长度积条件下ASE效应对放大器储能效率和小信号增益系数的影响。对4×2×3组合式放大器的计算结果表明：随着泵浦电压升高，ASE效应明显加强；23kV泵浦电压下，ASE效应造成的平均储能下降210%，小信号增益系数损耗为16.62%，增益不均匀性为7.44%；增益长度积可以作为判断ASE效应的依据，其值越大，ASE效应越强。     

高功率激光片状放大器中自发辐射放大研究

采用理论模拟和实验研究相结合的方法,研究了高功率激光片状放大器中的自发辐射放大(ASE)效应。建立了一套较完整的包含空间和时间的3维ASE模型,分析了不同电压、不同储能分布和不同泵浦时刻、不同增益长度积条件下ASE效应对放大器储能效率和小信号增益系数的影响。对4×2×3组合式放大器的计算结果表明：随着泵浦电压升高,ASE效应明显加强;23kV泵浦电压下,ASE效应造成的平均储能下降210%,小信号增益系数损耗为16.62%,增益不均匀性为7.44%;增益长度积可以作为判断ASE效应的依据,其值越大,ASE效应越强。     

旋转带电体和电磁场的角动量守恒定律及能量守恒定律

对均匀带电薄球壳匀加带旋转问题,由电磁场的角动量定恒守律和能量守恒定律两种方法分别得出了外力矩力其功率的正确正确结果。     

First-principles study of structural and elastic properties of CrO2 at high pressure

The structural and elastic properties of CrO₂ in the rutile phase under high pressures have been investigated using pseudopotential plane-wave method based on density functional theory. The optimized lattice parameters and the bulk modulus at zero pressure agree well with available experimental and theoretical data. The elastic constants C ₁₁, C ₁₂, C ₄₄, C ₃₃, C ₁₃, and C ₆₆ at zero pressure are calculated to be 359.91, 264.69, 143.28, 309.45, 218.45, and 260.74 GPa, respectively. Elastic constants, bulk modulus, shear modulus, Young's modulus, and Poisson's ratio under pressures are obtained. Our results indicate that the rutile phase is mechanically stable below 11.99 GPa. The elastic anisotropy of rutile phase under pressures has also been predicted.     

Influence of silicon doping density on vacuum field emission triode at high frequency range

Silicon FEA will affect the high frequency application of field emission tubes when it works at the microwave frequency range. This article shows that the electron emitting will be influenced by the majority carrier response time in semiconductor silicon. The surface capacitance and delay time of n-type and p-type silicon are calculated by using semiconductor theory. The result shows that the semiconductor conductivity will determine the maximum work frequency of device. The maximum work frequency (no considering other effects such as C_gc, g_m etc.) will be decreased from about 200 GHz to 2 GHz when the resistivity of p-type silicon is increased from 0.1 · cm to 10 cm.     

Surface order large deviations of phase interfaces for the continuum Widom-Rowlinson model in high density limit

We establish a surface order large deviation principle characterising, in the phase coexistence region, the exponential decay rates for the probabilities of macroscopic fluctuations of phase-separating interfaces for the continuum Widom-Rowlinson binary gas, with the thermodynamic and high fugacity limits taken simultaneously. The large deviation rate function is given by an isotropic surface energy functional and hence it attains its minimum for balls which are the most favourable shapes of ‘droplets’ of dominated phase within the ‘ocean’ of dominating phase.     

Structural and elastic properties of KBr at high pressure and high temperature

To study phase transition and elastic properties at high pressures and high temperatures, we have developed a realistic interaction potential model (RIPZ_pe) including temperature effects. This model is completely suitable for explaining the inter-atomic interaction involved at high temperature and high pressure as it includes the three-body interaction (TBI) and zero point energy effects. The phase transition of KBr crystal at high pressure and high temperatures including the TBI is done for the first time. We have estimated the phase transition pressures, volume collapses and elastic behaviour at various high pressure and high temperatures by RIPZ_pe approach and the results found are well suited with available experimental data.     

The probability of orbital angular momentum states of single photons with Z-tilt corrected residual aberration in a slant path turbulent atmosphere

With Rytov approximation and Kolmogorov spectrum model of index-of-refraction fluctuation, we study the effects of turbulence aberration on the orbital angular momentum of single photons in atmospheric communication channel. A theoretical model of measurement probabilities of orbital angular momentum states for single photons propagation under the Zernike tilt corrected slant path turbulent atmosphere channel is established. Our research shows that tilt-corrected residual aberration not only damage the initial OAM, but also induce new OAM. With the increasing of D/ρ₀, the number of the initial OAM photons will go down while the effective number of new OAM ascends. Meanwhile, the receiving probability of initial OAM photons declines, as the turbulence shifts from weak to strong. For Zernike tilt-corrected residual aberration, the receiving probability of initial OAM photons declines as the diameter of detector increases. The effect of Zernike tilt-corrected residual aberration on OAM of the photons is more larger than the effect of Zernike tilt turbulent aberration.     

Structural and elastic properties of barium chalcogenides (BaX,X=O,Se, Te) under high pressure

In the present paper we have investigated the high-pressure, structural phase transition of Barium chalcogenides (BaO, BaSe and BaTe) using a three-body interaction potential (MTBIP) approach, modified by incorporating covalency effects. Phase transition pressures are associated with a sudden collapse in volume. The phase transition pressures and associated volume collapses obtained from TBIP show a reasonably good agreement with experimental data. Here, the transition pressure, NaCl-CsCl structure increases with decreasing cation-to-anion radii ratio. In addition, the elastic constants and their combinations with pressure are also reported. It is found that TBP incorporating a covalency effect may predict the phase transition pressure, the elastic constants and the pressure derivatives of other chalcogenides as well.      

Pressure-induced phase transition and structural behavior of MgO at high temperatures: a model study

A realistic interaction potential model approach by including temperature effects is developed to study phase transition, elastic properties and thermo-physical properties at very high pressures and temperatures. This approach is effectively able to explain the inter-atomic interaction involved at high temperature and high pressure as it includes the three-body interactions. Earlier works overlooked the three-body interactions at high temperature and pressures. Moreover, the phase-transition pressures of MgO crystal at high temperatures including the three-body interaction are computed for the first time. Elastic behavior, anisotropic factor and Debye temperature of MgO at high pressures and temperatures are also reported.     

The influence of reverse energy transport on emission anisotropy in two-component viscous solutions

The effect of nonradiative reverse energy transport (NRET) in two donor-acceptor systems was studied experimentally. It was found that the NRET occurring in system I; rhodamine 6G (donor) and rhodamine B (acceptor), considerably lowers the emission anisotropy at medium and high concentrations. These results qualitatively confirm the predictions of the approximate theoretical approach of L. Kulak and C. Bojarski (see the preceding paper). In system II; rhodamine 6G (donor) and Nile Blue (acceptor), for which the NRET process does not occur, a good agreement with no-back-transport theory was obtained.     

The effect of electric field strength on electroplex emission at the interface of NPB/PBD organic light-emitting diodes

Organic light-emitting diode (OLED) based on two kinds of blue emission materials N,N′-bis(1-naphthyl)-N,N′-diphenyl-l,l′-diphenyl-4,4′-diamine (NPB) and 2-(4-biphenylyl)-5(4-tert-butyl-phenyl)-1,3,4-oxadiazole (PBD) was fabricated. There is only one emission peak in photoluminescence (PL) spectrum which originates from NPB exciton emission. And the electroluminescence (EL) emission peaks have an apparent red-shift with the increase of driving voltage. The red-shift emission from exciplex emission could be ruled out. Thus, by the method of Gaussian fitting it should be ascribed to the overlap of exciton emission and electroplex emission which occurs at the interface between NPB and PBD. The formation of the electroplex emission under high electric field is analyzed.