四能级原子系统中非线性电磁感应吸收的理论研究

在n型四能级原子系统中,研究了电磁感应吸收的非线性理论.结果表明:探测光的拉比频率和衰减分配系数A影响非线性吸收,进而影响介质吸收.当探测光光强较弱时,介质吸收和线性吸收一致,均表现为电磁感应吸收特征;当探测光光强增大时,介质吸收和线性吸收不再一致,介质吸收曲线将会呈现出烧孔现象;当探测光光强增大到控制光(或信号光)光强时,介质吸收表现出很大的增益现象.同时,非线性吸收受到衰减分配系数A的影响,即使在探测场很弱的条件下,随着A值的减小,介质吸收由电磁感应吸收现象表 关键词： 电磁感应吸收 非线性吸收 增益现象 n型四能级原子系统     

Co掺杂ZnO薄膜的湿化学法制备及其光致发光光谱

采用湿化学法在Si衬底上生长了纳米棒结构的Co掺杂ZnO薄膜,并研究了掺杂浓度对生成样品结构和性能的影响.研究表明这种湿化学法成本低廉、收益高、重复性良好.样品的XRD结果表明掺杂的ZnO没有出现杂相.SEM结果表明掺杂样品是由ZnO纳米棒团簇结构组成,且团簇的密度随着Co掺杂浓度的增大而增大.薄膜的光致发光光谱结果表明Co掺杂导致薄膜的带隙发生红移,同时也证明了Co原子有效地进入了ZnO晶格.     

密度泛函理论研究BeSin(n=1-12)团簇的结构、稳定性与电子性质

运用密度泛函理论(DFT),考虑多种初始构型下的自旋多重态,在B3LYP/6-311G基组水平上研究BeSi_n(n=1-12)团簇的平衡几何结构、电子性质、振动光谱与极化率.结果表明:BeSi_n团簇在基态附近有许多能量非常接近的同分异构体,且BeSi_n团簇的基态结构绝大多数为立体结构.n=1时,体系的基态为自旋三重态,n≥2时,则为单重态.铍原子的掺入使得主团簇的电子性质发生了明显的变化,掺杂使得体系的化学稳定性降低.BeSi₃,BeSi₅,BeSi₇与BeSi₉是幻数结构.团簇中原子间的成键相互作用随n的增大而增强.     

Mechanical and thermodynamic properties of the monoclinic and orthorhombic phases of SiC_2N_4 under high pressure from first principles

First principles calculations are preformed to systematically investigate the electronic structures, elastic and thermodynamic properties of the monoclinic and orthorhombic phases of Si C2N4 under pressure. The calculated structural parameters and elastic moduli are in good agreement with the available theoretical values at zero pressure. The elastic constants of the two phases under pressure are calculated by stress–strain method. It is found that both phases satisfy the mechanical stability criteria within 60 GPa. With the increase of pressure, the degree of the anisotropy decreases rapidly in the monoclinic phase, whereas it remains almost constant in the orthorhombic phase. Furthermore, using the hybrid density-functional theory, the monoclinic and orthorhombic phases are found to be wide band-gap semiconductors with band gaps of about 2.85 e V and 3.21 e V, respectively. The elastic moduli, ductile or brittle behaviors, compressional and shear wave velocities as well as Debye temperatures as a function of pressure in both phases are also investigated in detail.     

Origin8.0在普朗克常数测定实验中的应用

本文简单描述了Origin软件的主要功能,并以普朗克常数测定实验为例,介绍了Origin软件在近代物理实验中的数据处理过程.研究结果表明利用该软件处理物理实验数据能有效避免手工处理所带来的误差,并且能准确直观地处理实验数据.因此,作为一种常用数据处理方法非常适合在近代物理实验教学中使用.     

库仑滴定法测定酸雨中总氢离子浓度

本文用库仑滴定法结合Gran图,测定酸雨中的“自由氢离子”和“被束缚的氢离子”的总浓度。并对雨水中常出现的Fe~(3+)、Al~(3+)等离子的干扰影响也进行了探讨。并对10~(-4)～10~(-5)mol·L~(-1)浓度范围内标准硫酸溶液滴定结果进行了考察;以Gran函数((?)及(?)′)对滴定时间(t)作图,得一直线。相对误差在±5%左右。同时用该方法对武汉酸雨样品进行了实际测量。用标准加入法测得其回收率在90.8以上。     

Elastic and thermodynamic properties of vanadium nitride under pressure and the effect of metallic bonding on its hardness

By the particle-swarm optimization method, it is predicted that tetragonal P42mc, 141md, and orthorhombic Amm2 phases of vanadium nitride （VN） are energetically more stable than NaCl-type structure at 0 K. The enthalpies of the predicted three new VN phases, along with WC, NaC1, AsNi, CsCl type structures, are calculated each as a function of pressure. It is found that VN exhibits the WC-to-CsCl type phase transition at 256 GPa. For the considered seven crystal- lographic VN phases, the structures, elastic constants, bulk moduli, shear moduli, and Debye temperatures are investigated. Our calculated equilibrium structural parameters are in very good agreement with the available experimental results and the previous theoretical results for the NaC1 phase. The Debye temperatures of VN predicted three novel phases, which are all higher than those of the remaining structures. The elastic constants, thermodynamic properties, and elastic anisotropies of VN under pressure are obtained and the mechanical stabilities are analyzed in detail based on the mechanical stability criteria. Moreover, the effect of metallic bonding on the hardness of VN is also investigated, which shows that VNs in P42mc, 141md, and Amm2 phases are potential superhard phases. Further investigation on the experimental level is highly recommended to confirm our calculations presented in this paper.     

两步化学法制备Co掺杂ZnO薄膜及其磁性研究

采用电化学和湿化学法结合的两步化学法制备了Co掺杂的ZnO薄膜.X射线衍射(XRD)结果表明Co掺杂没有改变ZnO薄膜的六角纤锌矿结构.扫描电镜(SEM)和透射电镜(TEN)结果表明薄膜是由ZnO单晶纳米棒组成.X射线光电子能谱(XPS)结果表明Co2替代了Zn2+,实现了有效的掺杂.磁性测量的结果表明,样品在室温下的磁性表现为顺磁性和铁磁性的结合.     

ZnS:Cr2+中局域晶格结构和自旋单态对零场分裂参量的贡献

在统一配体场耦合图像的基础上,构造了d⁴电子组态过渡金属离子在强场图像下包括所有自旋状态的210×210维完全能量矩阵.通过对角化完全能量矩阵,研究了Cr²⁺掺杂ZnS的局域晶格结构和Jahn-Teller能.理论计算结果与实验值符合非常好.同时,还研究了Cr²⁺掺杂ZnS后体系自旋单态对零场分裂参量的贡献.结果表明:自旋单态对二阶零场分裂参量D的贡献可以忽略,但是对于四阶零场分裂参量a和F的贡献却 关键词： 2+')" href="#">ZnS:Cr²⁺ 统一配体场耦合 自旋单态 Jahn-Teller能