Magnetic,electrical transport and electron spin resonance studies of ferromagnetic insulating manganites Nd0.85Na0.15MnO3

We have investigated the magnetic, electrical transport and electron spin resonance (ESR) properties of polycrystalline Nd_0.85Na_0.15MnO₃ prepared by sol–gel method. A ferromagnetic–paramagnetic (FM–PM) transition is observed around 110 K, which is not accompanied by a metal–insulator transition. The sample displays the complete PM state associated with the ESR spectra fitted by single Lorentzian line shape above 130 K. Below 130 K, ESR spectra become distorted and then linewidth increases rapidly, where short-range magnetic order develops and coexists with PM phase due to the inhomogeneous magnetic state. In addition, the large difference between the activation energies obtained from the resistivity and ESR parameters (peak-to-peak linewidth and line intensity) at the frame of adiabatic small polaron hopping model is pointed out for Nd_0.85Na_0.15MnO₃.     

态|Ψ(3)〉q中广义磁场的不等幂次高次振幅压缩

利用多模压缩态理论,研究了一种新型的三态叠加多模叠加态光场|Ψ⁽³⁾〉_q中广义磁场分量(即第一正交相位分量)的不等幂次高次振幅压缩特性.结果表明:态|Ψ⁽³⁾〉_q是一种典型的三态叠加多模非经典光场,其广义磁场分量在一定条件下可呈现出周期性变化的、偶数次的不等幂次高次振幅压缩效应.     

全固态多波长飞秒脉冲激光系统

利用棱镜对引进频谱空间啁啾来补偿飞秒脉冲激光二次谐波产生中的相位失配,提高了倍频效率建立了一套全固态、多波长(1065nm, 532nm,823.1nm, 402nm)飞秒脉冲激光系统自制的Nd:YVO4激光器输出532nm绿光激光,最高平均功率可达5.6W当用2.5W绿光激光泵浦时,从自制的钛宝石激光器及经BBO倍频可分别输出中心波长为823.1nm和402nm,平均功率300mW和73mW,谱宽32.3nm和5.1nm,脉宽22fs和33.3fs、重复率108MHz的近红外和蓝光激光整个系统具有结构紧凑、倍频效率高、运行稳定的特点.     

丙氨酸咪唑钐的三维荧光激发和发射光谱

测量了新制丙氨酸咪唑钐水溶液的三维荧光激发和发射光谱,分析了在不同波长激发光作用下的荧光特征,与配体咪唑、α-丙氨酸及氯化钐的荧光谱进行了比较,讨论了模型化合物上转换荧光中的双光子和多光子加合现象并发现在10^-2-10^-4 mol/L 浓度范围内荧光强度与溶液浓度呈正相关.     

Zero—field—cooled and field—cooled magnetizations and magnetic susceptibility of itinerant ferromagnet SrRuO3

Zero-field-cooled(ZFC) magnetization,field-cooled(FC) magnetization,ac magnetic susceptibility and major hysteresis loops of itinerant ferromagnet SrRuO3 have been measured at magnetic ordering temperatures ranging from 5 to 160K.An empirical model is proposed to calculate the measured ZFC magnetization.The result indicates that the calculated ZFC magnetization compares well with the measured one.Based on the generalized Preisach model.both the ZFC and FC curves are reproduced by numerical simulations.The critical temperature and critical exponents are determined by measuring the ac magnetic susceptibility in different bias magnetic fields at temperatures in the vicinity of the point of phase transition.     

锂洞原子双激发态的鞍点能量计算

采用鞍点截断变分方法和鞍点复数转动技术,计算和分析了锂洞原子双激发共振态[1s(2s2p)3P]2P0的鞍点能量和波函数.计算结果表明这种理论计算方法是获得高精度的能量值的重要保证.     

改进型低阻类膜片加载同轴渡越时间振荡器

采用2.5维粒子模拟软件对改进型低阻类膜片加载同轴渡越时间振荡器进行了研究。研究结果表明：提取腔工作于类模场时,具有较高的束波互作用效率;引入渐变型输出波导,提高了提取腔内微波向外耦合输出的能力;通过加载感性支撑杆,一方面对金属膜片起支撑固定作用,另一方面可以及时将膜片上的感应电荷导流至接地外筒、从而降低间隙附近的空间电荷效应,以增加可提取的束动能。经优化设计,该结构在二极管电压为530 kV,二极管电流为12.9 kA、外加导引磁场为0.5 T的条件下,输出微波功率2.74 GW,微波频率7.76 GHz,束波功率转换效率达40%。     

Spectrophotometric Study of Catechol Oxidation by Aerial O2 in Alkaline Aqueous Solutions Containing Mg(II) Ions.

Electronic absorption spectroscopy was employed to study the aerial oxidation of catechol (1,2-benzenediol) in alkaline aqueous solution containing an excess of Mg(II) ions. Graphical analysis by the matrix method of UV spectra recorded at regular time intervals gave a good fit for two absorbing species in solution. Based on this result and our earlier ESR spectroscopic investigations we concluded that two main absorbing species in this system are Mg(II)-spin stabilized o-benzosemiquinone anion radical and C-C dimer formed by the nucleophilic attack of catecholate anion on o-benzoquinone. Although the formation of 1,2,4-benzenetriol during the catechol oxidation has been detected in some ESR studies its presence was not indicated by this analysis probably because of the low and/or stable steady state concentration throughout the experiment.     

光子晶体平面波导与脊波导高效耦合技术的研究

利用一维变周期谐振腔阵列和非线性缓变边界，可以实现光波从脊波导到光子晶体平面波导 （PCW）的高效耦合.基于平面波展开法（PWE）和时域有限差分法（FDTD），深入分析和讨 论了普通脊波导、2D-PCW结构和本征模以及工作模式、缓变边界形状等对耦合效率的影响， 从而得出光波从脊波导到2D-PCW、再返回脊波导的统一图景.指出考虑模式转换和采用缓变 边界条件可以极大提高PCW与脊波导间的耦合效率.对PC-PW边界采用线性和非线性缓变结构 进行了仿真，讨论了边界缓变程度对耦合效率的影响.结果表明，采用模式耦合和PC-PW余弦 缓变边界时的耦合效率在较宽的带宽内超过了95%. 关键词： 光子晶体波导 脊波导 PWE FDTD 耦合边界     

糠醇辅助的聚合凝胶法制备纳米Li4Ti5O12负极材料

以硝酸锂、钛酸正丁酯和糠醇为反应物,采用糠醇聚合凝胶法制备了纳米Li₄Ti₅O₁₂粉体．利用XRD、SEM和BET比表面测试对产物进行了表征,并研究了纳米Li₄Ti₅O₁₂粉体作为锂离子电池负极材料的电化学性能．在700℃或更高温度烧结时产物为纯相的尖晶石型．通过柠檬酸、聚乙烯吡咯烷酮、十六烷基三甲基溴化铵(CTAB)表面活性剂的加入能够减少产物颗粒的团聚程度,增大粉体的比表面积,提高其电化学性能．加入0.5 g CTAB、700℃烧结12 h的Li₄Ti₅O₁₂粉体展示出最高的比容量和最佳的循环性能,10 C下充电比容量高达156.7 mAh/g．