Kr原子偶宇称4p^5（^2P1／2）nl’[K，]J（l＇=1，3）自电离态共振增强激发光谱线形研究

在单光子29000～40000cm^-1。能量范围内,获得亚稳态4p55s[3／2]2和4p^5s’[1／2]oKr原子向其4p5npr[3／2]1．2,[1／2]1和4p5nfr[5／2]3序列自电离Rydberg态跃迁的共振增强激发光谱,光谱线宽≈0．1cm^-1．这些偶宇称自电离态的激发谱呈现明显的不对称线形,如此高分辨的激发谱大部分是首次报道．根据Fano线形关系对激发谱进行系统地分析,获得许多新的系统的能级位置、量子亏损、线性因子、共振宽度、共振态寿命和衰减宽度等数据,基于实验拟合所得的系统参数,我们发现线形因子和共振宽度相对有效量子数呈线性关系．另外还分析了4p^5np＇序列的能级间距．     

Electro-optical properties of planar nematic cells impregnated with carbon nanosolids

We report electro-optical effects in planar-aligned liquid-crystal cells of pristine and doped calamitics in the presence of dc voltage. The doped cells comprise both a nematic host and a minute amount of either buckminsterfullerene or multiwalled carbon nanotubes. The voltage–transmittance and voltage–capacitance hystereses were observed from the sample cells in the range of applied dc voltage up to 8 V. Experimental evidence indicates that a nanoscale carbon dopant can affect the behavior of a nematic in terms of ion-charge effects and that doping with nanotubes can effectively reduce the driving voltage.     

氪灯发光总功率和氙灯发光总能量检测设备

根据氪灯、氙灯发光的工作原理,介绍了氪灯发光总功率和氙灯发光总能量检测系统。该系统可以对氪灯发光总功率和氙灯发光总能量进行批量检验,使用户能在相关激光产品的生产和装配过程中对其进行质量控制,从而提高了激光产品的合格率,缩短了生产时间。在连续氪灯和脉冲氙灯的入厂检验中,氪灯发光总功率和氙灯发光总能量是需要检测的主要技术指标。新型氪灯、氙灯性能综合检测系统是通过采用积分球、功率计以及能量计来检测氪灯的发光总功率和氙灯的发光总能量的。设备由:积分球、功率计、能量计、氪灯和氙灯支架及冷却系统、氪灯和氙灯电源等五部分组成。     

Convex‐round graphs are circular‐perfect

We show a connection between two concepts that have hitherto been investigated separately, namely convex‐round graphs and circular cliques. The connections are twofold. We prove that the circular cliques are precisely the cores of convex‐round graphs; this implies that convex‐round graphs are circular‐perfect, a concept introduced recently by Zhu [10]. Secondly, we characterize maximal K_r‐free convex‐round graphs and show that they can be obtained from certain circular cliques in a simple fashion. Our proofs rely on several structural properties of convex‐round graphs. © 2002 Wiley Periodicals, Inc. J Graph Theory 40: 182–194, 2002     

Surface and interface optical phonon modes and electron-phonon interaction in a multi-shell spherical system

Within the framework of the dielectric continuum model, interface optical(IO) and surface optical(SO) phonon modes and the Fr?hlich electron-IO (SO) phonon interaction Hamiltonian in a multi-shell spherical system were derived and studied. Numerical calculation on CdS/HgS/H₂O and CdS/HgS/CdS/H₂O spherical systems have been performed. Results reveal that there are two IO modes and one SO mode for the CdS/HgS/H₂O system, one SO mode and four IO modes whose frequencies approach the IO phonon frequencies of the single CdS/HgS heterostructure with the increasing of the quantum number l for CdS/HgS/CdS/H₂O. It also showed that smaller l and SO phonon compared with IO phonon, have more significant contribution to the electron-IO (SO) phonon interaction. Received 16 October 2001 and Received in final form 23 January 2002 Published online 25 June 2002     

Polarized infrared reflectivity study of an oriented ceramic of Bi 2 Sr 2 Ca 2 Cu 3 O 10 + δ (Bi-2223)

The reflectivity spectra of an oriented ceramic of Bi-2223 has been investigated by polarized infrared reflectivity spectroscopy in the energy range 0.005-2.2 eV. It is shown that the data for the polarization parallel to the c axis cannot be fitted with a one-component Drude or extended-Drude model. The conductivity spectrum is then obtained from the best fit of a “double-damping Drude” model to reflectivity spectra, itself derived from the factorized form of the dielectric function, and by a Kramers-Kronig inversion as well. The data and their analysis give a new insight of the 2D character of the system. Received 26 April 2001 and Received in final form 28 August 2001     

The stability of magnetobipolarons in low-dimensional systems

We investigate the stability condition of large bipolarons confined in a parabolic potential containing certain parameters and a uniform magnetic field. The variational wave function is constructed as a product form of electronic parts, consisting of center of mass and internal motion, and a part of coherent phonons generated by Lee-Low-Pines transformation from the vacuum. An analytical expression for the bipolaron energy is found, from which the ground and excited-state energies are obtained numerically by minimization procedure. The bipolaron stability region is determined by comparing the bipolaron energy with those of two separate polarons, which is already calculated within the same approximation. It is shown that the results obtained for the ground state energy of bipolarons reduce to the existing works in zero magnetic field. In the presence of a magnetic field, the stability of bipolarons is examined, for three types of low-dimensional system, as function of certain parameters, such as the magnetic-field, the electron-phonon coupling constant, Coulomb repulsion and the confinement strength. Numerical solutions for the energy levels of the ground and first excited states are examined as functions of the same parameters. Received 7 March 2002 and Received in final form 22 April 2002 Published online 25 June 2002     

A simple theory of 40 K superconductivity in MgB2: first-principles calculations of Tc, its dependence on boron mass and pressure

We have studied the superconducting properties of MgB₂ from first-principles under isotropic, uniaxial, and biaxial compressions. We find that the in-plane boron phonons near the zone-center are very anharmonic and strongly coupled to the planar B σ bands near the Fermi level. This mode is found to be the key to quantitatively explain the observed high T_c, the total isotope effect and the pressure dependence of T_c. We propose that a stringent test on the hole and phonon based theories of the superconductivity in MgB₂ would be a measurement of the biaxial ab-compression dependence of T_c.     

Kr和Kr2的实验和理论研究

利用超声分子束技术、同步辐射和反射式飞行时间质谱仪得到了Kr和Kr2的光电离质谱和光电离效率谱, 确定了Kr和Kr2的电离能. 利用Gaussian-03程序中的MP2(Full)/6-31G*, QCISD/cc-pVTZ以及B3LYP/6-31G方法优化了Kr2的结构, 计算了它们的振动频率和电离能, 计算结果显示: 当采用相同的理论水平和基组时, 随着Kr同位素质荷比(m/z)的增大, 它们结构和电离能保持不变, 而振动频率逐渐变小. 与此同时, 用G2方法计算了Kr (84)和Kr2 (168)的电离能, 它们的电离能的理论值与实验结果符合得比较好.     

Two new Weyl-type bounds for the Dirichlet Laplacian

In this paper, we prove two new Weyl-type upper estimates for the eigenvalues of the Dirichlet Laplacian. As a consequence, we obtain the following lower bounds for its counting function. For , one has

and

where

is a constant which depends on , the dimension of the underlying space, and Bessel functions and their zeros.