NⅡ离子2p4f—2p3d辐射跃迁概率的理论研究

在全相对论理论框架下，利用多组态Dirac-Fock(MCDF)方法，系统计算了NⅡ离子2p4f—2p3d的辐射跃迁概率，得到的结果与已有实验值符合很好.具体计算中，详细分析了相对论效应、电子关联、弛豫效应、Breit相互作用和量子电动力学(QED)效应对能级精细结构及辐射跃迁概率的影响.结果表明：相对论效应、电子关联和弛豫效应对NⅡ 2p4f-2p3d辐射跃迁概率有很重要的影响,考虑了这些效应后计算值得到明显改善.     

Charge order and spin order in Nd_(0.5)Sr_(0.5)Mn_(1-x)(Ga_x, Ti_x)O_3 system

Magnetic properties of Nd_(0.5)Sr_(0.5)Mn_(1-x)(Ga_x, Ti_x)O_3 system (0.04≤x≤0.4) were inves- tigated through magnetization and electron spin resonance (ESR) measurements. It was observed that a small amount of Ti substitution for Mn will destroy the charge-ordering (CO) phase completely and induce the cluster-spin-glass phase in the system, which displays a procedure of collapse of CO and of an enhancement of spin ordering (SO) phase. In contrast, the Ga substitution for Mn induces a melt- ing of CO phase in the system. It was observed that with substitution the CO phase is suppressed gradually and the remanent CO phase is retained all the while, and withal, there is a co-existence of AFM CO phase and FM SO at low temperature. In addition, an abrupt rise of magnetization was observed in M-T curves. We attributed this abnormal phenomenon to a transition from canted AFM SO to FM SO in CO region.     

Critical Behavior of the Blume-Emery-Griffiths Model for a Simple Cubic Lattice on the Cellular Automaton

The spin-1 Ising model with the nearest-neighbour bilinear and biquadratic interactions and single-ion anisotropy is simulated on a cellular automaton which improved from the Creutz cellular automaton (CCA) for a simple cubic lattice. The simulations have been made for several k=K/J and d=D/J in the 0≤d<3 and −2≤k≤0 parameter regions. We confirm the existence of the re-entrant and the successive re-entrant phase transitions near the phase boundary. The phase diagrams characterizing phase transitions are presented for comparison with those obtained from other calculations. The static critical exponents are estimated within the framework of the finite-size scaling theory at d=0, 1 and 2 in the interval −2≤k≤0. The results are compatible with the universal Ising critical behavior.     

失谐对耗散耦合腔阵列体系超流-绝缘相变的影响

利用平均场理论和微扰论解析求解了失谐存在且环境作用下Jaynes-Cummings-Hubbard模型的哈密顿量,得到了体系序参量的解析表达式,并讨论了失谐对体系超流一绝缘相变的影响,研究结果表明:调节失谐可以改变腔间的有效排斥势和系统的临界隧穿率,实现系统在超流态和绝缘态之间转变,结合耗散耦合腔阵列的输运性质探讨了失谐对序参量取值的影响,结果显示:沿失谐负支随着失谐的增大,序参量会经历先增后减的变化。     

A note on a pioneering work in quantitative spectroscopy: UV bands of the hydroxyl radical

The publication by G.H. Dieke and H.M. Crosswhite (JQSRT 1962;2:97-199) is a classic paper detailing the spectroscopy of the A²Σ⁺←X²Π bands of the hydroxyl radical (OH) in the ultraviolet region. It soon became the basis of astrophysical modeling, most subsequent theoretical and laboratory studies of the OH individual line parameters, and a host of other applications.     

Double peaks on ac magnetization in a superconducting Pb-porous glass nanocomposite

Studies of temperature dependences of ac magnetization were carried out for a superconducting lead-porous glass nanocomposite. Double peaks were found on the imaginary part of ac magnetization which were accompanied with double steps on the real part. The lower-temperature anomalies in ac magnetization differed noticeably when they were obtained upon cooling and warming. The double peaks were treated as two phase transitions in the vortex system: the liquid-solid transition which occurs close to the onset of superconductivity and solid-solid one which is triggered by superconductivity in confined lead islands.     

Effect of magnetic fields on the linear and nonlinear intersubband optical absorption coefficients and refractive index changes in square and graded quantum wells

In this study, both the intersubband optical absorption coefficients and the refractive index changes as dependent on the magnetic field are calculated in square and graded quantum wells. Our results show that the position and the magnitude of the linear and total absorption coefficients and refractive index changes depend on the magnetic field strength and the shape of potential. The incident optical intensity has a great effect on the total absorption and refractive index changes.     

循环跃迁的Δ 型三能级系统中的无反转激光

研究了在引入非相干抽运的情况下,循环跃迁的Δ型共振三能级系统中产生的无反转激光.利用主方程的方法, 导出了缀饰态中强相干场极限下布居数项和相干项的稳态近似解析解以及产生无反转激光所需要满足的条件;并利用数值模拟的方法讨论了布居数分布、 系统增益对探测场和相干场拉比频率的依赖性以及随时间的演化规律. 结果表明:无论各个参量取何值,共振Δ型三能级系统总是处于无粒子数反转的状态; 只要探测场或相干场之中有一个为强场,便可产生无反转激光; 当其中任意一个场远强于另一个场时,系统的无反转增益将不再依赖于任何一个场的拉比频率.     

Critical entanglement and geometric phase of a two-qubitmodel with Dzyaloshinski--Moriya anisotropic interaction

We consider a two-qubit system described by the Heisenberg XY model with Dzyaloshinski--Moriya (DM) anisotropic interaction in a perpendicular magnetic field to investigate the relation between entanglement, geometric phase and quantum phase transition (QPT). It is shown that the DM interaction has an effect on the critical boundary. The combination of entanglement and geometric phase may characterize QPT completely. Their jumps mean that the occurrence of QPT and inversely the QPT at the critical point at least corresponds to a jump of one of them.