CaWO4晶体中F型色心电子结构的研究

运用相对论的密度泛函离散变分法(DV-Xa)研究了CaWO4晶体中F型色心的电子结构.计算结果表明,F和F+心在禁带中引入了新的施主能级;分析了晶体内可能存在的光学跃迁模式,并通过过渡态的方法计算了F,F+心跃迁到导带底的能量分别为1.92 eV和2.42 eV.因此,从理论上推断了F和F+心在CaWO4晶体中可能引起650nm和515 nm的吸收,由此说明CaWO4晶体中650 nm和515 nm吸收带起源于晶体中的F和F+心.     

Local Lattice Distortion Around VPb^2- in PbWO4 and the Origin of the 420nm Luminescence Band

The lattice structures around one lead vacancy VPb^2- in PbWO4 are studied within the framework of the fullrelativistic density functional theory. Using the conjugate gradient method, we optimize the geometry of the ions around VPb^2- by moving the ions within the sub-cell until specified tolerance is satisfied. We obtain the geometric positions of ions around VPb^2- after optimization. The calculated results indicate that there would be local lattice distortion caused by the existence of VPb^2-. The electronic structures of both the optimized and pre-optimized PWO containing VPb^2- have been calculated. The density of states of the distorted PWO indicates that the energy gap between the 2p state of O^2- and the 5d state of W^6 is 3.90eV, which shows that the distorted W-O tetrahedron may be the 42Onm luminescence centre.     

类Ne钛X射线激光输出特性实验

在星光激光装置上, 使用X射线多层膜反射镜、铝滤片及X射线CCD探测器组成高灵敏度空间分辨探测系统, 对用预脉冲技术产生的类Ne钛单线 (J=0-1, 3p-3s跃迁)软X射线激光输出特性进行了测量。由实验得到了类Ne钛X 射线激光束近场与距靶端32mm处(准远场)强度的空间分布, 给出了该激光束在近场强度最大区域的空间尺度(FWHM)约为72μm×31μm, 以及在垂直靶面与平行靶面方向的束发散角分别约为4mrad与9mrad。     

可变入射距离平焦场谱仪的概念设计

从理论上证明了可变入射距离的平焦场软X射线谱仪设计的可行性。对于标称栅距σ0＝（1/1200）mm和象差修正项M20＝-20/R, R分别为5649和6000mm的光栅, 对不同的入射距离, 计算出与平焦场相对应的入射角和成象距离, 使一定波长范围内的光谱可以被聚焦在一个平面上,从而提高了变栅距光栅使用的灵活性。同时可通过取消谱仪中入射狭缝, 使谱仪的光通量提高约1个量级。     

First Principles Study on Electronic Structures of Mn^2＋：CdMoO4 Crystals

Electronic structures of the Mn^2＋ ：CdMoO4 crystal axe studied within the framework of the fully relativistic self-consistent Dirac Slater theory, using a numerically discrete variation （DV-Xα） method. The calculated results indicate that the 3d states of Mn have donor energy level in the forbidden band of CdMoO4 crystal. The O^2- transition energy of O 2p→Mn 3d is 3.12eV under excitation corresponding electronic transition being O^2-＋Mn^2＋→↑hvex=3.12 eV O^-- ＋Mn^＋→↑hvem O^2-＋Mn^2＋. It is predicted that the wavelength of emission should be located in the range of the 500-600nm. Thus the 500-600mm emission bands peaking at 550nm （2.25eV） of CdMoO4 crystal under excitation may be related to the Mn-like dopant ion in CdMoO4 crystal.     

非整数量子跃迁

证明频率为v的辐射引起的量子跃迁中,跃迁系统始末两态能量差不必是hv的整数倍。跃迁的玻尔条件和光电效应的爱因斯坦定律都是微扰近似的结果,在强激光引起的跃迁中不成立。We prove that in the quantum transition of a system induced by the radiation of frequency v, the energy difference between the initial and the final states of the system is not necessarily being an integer multiple of hv. The Bohr condition for quantum transitions and the Einstein law for photo-electric effects are approximate results of perturbation. They are violated in the transitions induced by intense lasers.     

PbWO4晶体中的填隙氧及其对晶体光学性质的影响

运用GULP计算软件模拟计算了PbWO₄(PWO)晶体中不同位置的填隙氧原子点缺陷的生成能，计算结果表明：当填隙氧原子存在于(WO₄)^2-的周围时，填隙氧原子点缺陷的生成能最低；进一步运用基于密度泛函理论的全数值自洽DV-Xα方法计算了包含填隙氧原子的PWO晶体的态密度，计算结果表明：当填隙氧处在(WO₄)^2-的周围时，容易与(WO₄)^2-上的一个或两个氧离子相互作用形成分子离子O₂^2-或O₃^4-，通过分析这些计算结果，认为PWO晶体中350 nm吸收带的出现很可能与晶体中的氧分子离子有关.     

类氖钛软X射线激光空间发射区域研究

使用高分辨平焦场谱仪，在“星光”激光器上，对类氖钛J=0—1，3p—3s跃迁32.6nm软X射线激光空间发射区域进行了实验测量，并与LASNEX和XRASER程序模拟结果作了比较．实验采用预脉冲打靶技术，预、主脉冲时间间隔5ns，峰值能量比为1%．结果表明：当驱动能量在50—150J范围内变化时，等离子体介质中X射线激光发射区与驱动能量大小密切相关，并随之增大而增大 关键词：     

关于K-p两体问题的相对论修正

从基本理论出发，导出并求解了含有相对论修正的K^-介子与质子的两体薛定谔方程。其解可看作有统计解释的波函数。计算了K^p的散射长度，结果表明相对论效应是很明显的。A two-body equation of the kaon-proton system with relativistic correction is derived and solved. The solution can be considered as a wave function with the probability interpretation. The scattering lengths are calculated, and the numerical result shows that the relativistic effect is apparent.     

氢键质子的运动与胞嘧啶的变异几率

运用Gaussian98 MP2/6 311G(d， p)级的从头计算法计算了DNA分子中胞嘧啶碱基中H13质子的势能曲面。 发现有两个势阱: 其中一个对应正常的胞嘧啶， 而另一个则对应它的顺式亚胺式互变异构体。 质子在这两个势阱的束缚对热扰动是稳定的。 质子在势阱中像单摆一样绕着离它最近的氮原子摆动， 还可以远离氮原子与其它碱基形成氢键。 估算出的H13质子从一个势阱到另一个势阱的穿透几率表明质子呆在其中一个势阱中的寿命大约是6×102 a， 这使胞嘧啶和它的顺式亚胺式互变异构体在室温气相实验中远不能达到热平衡。 对这些结果的生物学意义作了讨论。 The potential energy surface of the H13 proton in base cytosine of theDNA molecules is calculated ab initio at the Gaussian98 MP2/6 311G(d， p) level. Two potential wells are found. One corre sponds to the normal cytosine， while the other corresponds to its imino tautomer. The bindings of the proton in these wells are stable enough against the thermo disturbance. The motions of the proton in these wells are oscillations around the nearest nitrogen atom like the pendulum， and may move far away from the nitrogen atom to form the hydrogen bond with other bases. The estimated tunneling probability of the H13 proton from one well to another well shows that the life time of the proton staying in one of these wells is about 6×102 a. It is too long to let tautomers of cytosine be in thermodynamical equilibrium in a room temperature gas phase experiment. The biological significance of these results is discussed.