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971.
Making use of the adiabatic hyperspherical approach, we report a calculation for the energy spectrum of the ground and low-excited states of a two-dimensional hydrogen negative ion H^{-} in a magnetic field. The results show that the ground and low-excited states of H^{-} in low-dimensional space are more stable than those in three-dimensional space and there may exist more bound states. 相似文献
972.
The dynamics of a semiconductor laser with two optical feedbacks is studied in this paper. A new set of nonlinear rate equations that can describe external cavity semiconductor lasers with any amount of two optical feedbacks is proposed. It is found that when the laser is biased above the threshold and subjected to one feedback, the other feedback can induce low-frequency fluctuations. 相似文献
973.
近几年在对远离核的实验研究中,观测到了理论预言的新衰变模式,如45Fe的双质子衰变,β-缓发裂变;对中子滴线外一些核的存在可能性也进行了较多的实验探索和理论分析;开始了对人们一直关注的中子集团存在可能性的实验探索.远离核谱学和衰变性质研究逐渐深入,通过对一些远离核第一激发态能量的系统比较和许多远离核β衰变Q值的测量,以及核质量的精确测量,发现在远离核区,原有的一些幻数消失,代之产生了一些新的幻数,对其产生原因的理论分析做了简要的综述. Recently the predicted new decay model, for instance two-proton decay and β~(-)delayed fission have been observed in the investigations of the nuclei far from stability line. The existence of the nuclei located beyond the drip-line has already been studied experimentally and theoretically. It has been started to search for the neutron cluster in experiment by using neutron-rich nuclei. The researches of the spectroscopy and decay properties of the nuclei far from stability line are more and deeper, and... 相似文献
974.
Molecular Chirality and Chiral Superlattice in Crystal of Tetrakis[(pyrrol-1-yl)methyl]methane 总被引:3,自引:0,他引:3
XU Wei ** LU Yin-xiang LIU Chun-ming LAN Bi-jian ZHOU Hui WANG Jing-mei . Department of Materials Science Fudan University Shanghai P. R. China . Research Center for Analysis Measurement Fudan University Shanghai P. R. China 《高等学校化学研究》2004,20(6):778-780
The crystal structure of tetrakis[(pyrrol-1-yl)methyl]methane was determined by X-ray diffraction measurement, and the result shows that it belongs to monoclinic crystal system, space group is P21/n, with a=0.9284(3) nm, b=1.0950(6) nm, c=1.8749(8) nm; α=γ= 90.00(4)°, β=103.63(3)°, V=1.8523(14) nm3, Z=4, ρcalcd.=1.192 kg/m3, μ=0.072 nm-1, F(000)=712, R1=0.0854, wR2=0.1884. It has been found that the molecules exist in two enantiomeric states. Enantioselective self-assemblies such as one-dimensional molecular stacks in a single handedness, homochiral monolayers and a chiral superlattice are specified in this racemic crystal. In addition, a simple technique is advocated to distinguish chiral states from tetrahedral molecules in the solid state. The present R/S nomenclature of the tetracooradinated carbon centers is used solely for its convenience to distinguish the two enantiomeric states, but not used to determine the absolute configurations. 相似文献
975.
三维Ising模型的蒙特卡罗模拟 总被引:1,自引:0,他引:1
采用蒙特卡罗(Monte Carlo)重点抽样法对三维Ising模型进行计算机模拟,测量无外磁场时三维Ising模型中自旋键链的能量、磁化强度、比热及磁化率的统计平均值与标准误差(不确定度).结果表明,三维Ising模型在无外磁场时存在自发磁化现象,铁磁→非铁磁相变临界点在J/(kBTC)=0.222 0,或居里温度TC=4.500 0处.并研究存在外磁场时上述物理量随温度与外磁场的变化规律,给出物理解释. 相似文献
976.
Magnetization of two-dimensional heavy holes with boundaries in a perpendicular magnetic field 下载免费PDF全文
The magnetisation of heavy holes in III--V semiconductor quantum
wells with Rashba spin-orbit coupling (SOC) in an external
perpendicular magnetic field is studied theoretically. We
concentrate on the effects on the magnetisation induced by the
system boundary, the Rashba SOC and the temperature. It is found
that the sawtooth-like de Haas--van Alphen (dHvA) oscillations of
the magnetisation will change dramatically in the presence of such
three factors. Especially, the effects of the edge states and Rashba
SOC on the magnetisation are more evident when the magnetic field is
smaller. The oscillation center will shift when the boundary effect
is considered and the Rashba SOC will bring beating patterns to the
dHvA oscillations. These effects on the dHvA oscillations are
preferably observed at low temperatures. With increasing
temperature, the dHvA oscillations turn to be blurred and eventually
disappear. 相似文献
977.
978.
The generalized thermo-elasticity theory, i.e., Green and Naghdi (G-N) Ⅲ theory, with energy dissipation (TEWED) is employed in the study of time-harmonic plane wave propagation in an unbounded, perfectly electrically conducting elastic medium subject to primary uniform magnetic field. A more general dispersion equation with com- plex coefficients is obtained for coupled magneto-thermo-elastic wave solved in complex domain by using the Leguerre's method. It reveals that the coupled magneto-thermoelastic wave corresponds to modified dilatational and thermal wave propagation with finite speeds modified by finite thermal wave speeds, thermo-elastic coupling, thermal diffusivity, and the external magnetic field. Numerical results for a copper-like material are presented. 相似文献
979.
980.