类碳体系基态能量的精细结构(英文)

以多电子原子精细结构哈密顿的球张量形式和不可约张量理论为基础,建立了计算多电子原子精细结构(包括自旋-轨道相互作用、自旋-其它轨道相互作用和自旋-自旋相互作用)能量的一般性解析理论形式,应用所建立的理论对类碳体系(Z=6～8)基态的精细结构能量进行了具体计算,计算结果与实验数据符合得较好.     

Intercombination transitions of the carbon-like isoelectronic sequence

Energy levels, wavelengths, transition rates, oscillator strengths, and lifetimes between the 2s22p23P1,2s22p23P2,and 2s2p35S2 levels of ions in the carbon-like (C-like) isoelectronic sequence (nuclear charges Z=7-92) are calculated in the valence and core-valence limits using the multiconfiguration Dirac-Fock method. The Breit interaction, quantum electrodynamics (QED), and finite nuclear mass effects are taken into account in subsequent relativistic configuration-interaction calculations. The calculated energies and transition rates are compared with the critically evaluated experimental values and other recent calculated results. Our calculated data are in good agreement with these data.     

Density dependence of solar emission lines of carbon-like ions

Steady state level population of 15 levels of carbon-like ions: NeV, MgVII, SiIX, and SXI have been computed as a function of electron density and temperature taking into account collisional processes and spontaneous radiative ones. Photo-excitation among the ground term levels has also been considered. Knowing the level density, line intensities have been computed as a function of electron density and temperature. This study indicates that line intensity ratios for carbon-like ions can be used as a diagnostic in the determination of these two parameters of the solar plasma. The resulting line fluxes from these ions at earth distance are compared with observation. Presented at the 5th Annual Radio and Space Sciences Symposium, National Physical Laboratory New Delhi, January 1979.     

Atomic parameters for Fe(XV) and Ni(XVII)

Transition probabilities and collision strengths are tabulated, between the fourteen lowest levels of the magnesium-like ions Fe(XV) and Ni(XVII), for use in calculations of line intensities radiated from laboratory and astrophysical plasmas.     

类碳体系基态能量的相对论修正(英文)

以Breit-Pauli哈密顿的球张量形式为基础,借助不可约张量理论,将多电子原子能量的相对论修正理论拓展到了原子的拉卡波函数为多个Slater基函数的线性组合的情形,导出了此情形下多电子原子能量相对论修正(包括相对论质量修正项、单体和双体迭尔文修正项、自旋-自旋接触相互作用项)的解析表达式,完成了所有角向积分和自旋求和计算.利用所建立的理论,对类碳体系基态能量的相对论修正进行了具体计算.     

Atomic parameters and rate coefficients for selected transitions in A1(XII)

Improved values for the electron impact excitation Gaunt factor, cross section and rate coefficients are obtained in the distorted wave approximation for the 1s→np and 2s→np (n ? 5) transitions in A1(XII). Also presented are the results of calculations for the oscillator strength for these transitions.     

Atomic quadrupolar photoemission asymmetry parameters from a solid state measurement

A method for measuring the asymmetry parameter gamma arising from dipole-quadrupole interference in core-level photoemission is proposed which is based on condensed thin films and exploits the influence of this asymmetry in photoemission monitoring of x-ray standing wave field absorption. The high density of material in this method offers some advantages over a conventional gas-phase measurement. Results are presented for C, O, and F 1s photoemission at photon energies around 3 keV. The combined nondipole asymmetry factor (delta+gamma/3) for non- s-states can be determined in a similar way.     

Determining noise parameters of MESFET''s solely from their S parameters

A method for determining the noise parameters of MESFET's solely from their S parameters is presented in this paper. The enhanced Johnson noise, the diffusion noise, the thermal noise, the influences of bias condition, the effect of parastic resistances and the aftermath of package are all taken into consideration in the noise model. The calculating results of our method agree very well with the measured data. This method can be employed rapidly, conveniently, both at the wafer stage of device fabrication and to packaged devices.List of symbols a Thickness of the active layer - b Undepleted channel width - C, Cr Correlation coefficient - C_c Coupling capacitance - C_cg, C_cd, C_sg, C_sd Fringing capacitances - C_dc Drain-channel feedback capacitance - C_gs Gate-source capacitance - C_gd Gate-drain feedback capacitance - D The high field diffusion constant, =35cm²/sec - F_min Minimum noise figure - g_gn, g_dn Equivalent noise conductance - g_m Transconductance - I_ds Drain-to-source current - k Boltzmann's constant, =1.38×10^–23J/°K - L Gate length - L_dom Length of high-field domain - L_g, L_d, L_s Inductances of bond wire - N_D Doping density - q Electronic charge, =1.6×10^–19C - r_d Drain resistance - R_ds Output resistance of MESFET - R_g, R_d, R_s Resistances of bond wire - R_gs Ohmic resistance of a gate-source portion of a FET - R_n Equivalent noise resistance - S Scattering parameters - s Bias parameter, - S _io Spectral density - T Reference temperature - V_bl Built-in diffusion potential - V_ds Drain-source voltage - V_gs Gate-source voltage - V_nd Open-circuit noise voltage at drain - O _s Saturation velocity - W Gate width - x_i ith element of the equivalent circuit - Y_cor Correlation admittance - Y_i,j Four MESFET Y parameters corresponding to S parameters - Y_i,j MESFET Y parameters calculated from its equivalent circuit - Y_opt Optimum signal source admittance - _O Permittivity of free space - _r Realitive dielectric constant - Low field mobility - Transit time - f Narrow frequency interval Graduate student currently working toward the M.S. degree     

Elimination of metal catalyst and carbon-like impurities from single-wall carbon nanotube raw material

The purification of as-produced single-wall carbon nanotube (SWCNT) material is one important step in order to make the material optimally suited for a number of potential applications. We present a purification procedure based upon oxidation of the raw material in oxygen atmosphere at elevated temperatures and a subsequent treatment in HCl. It is shown that this procedure results in the removal of the majority of the impurities comprising carbonaceous species and metal catalyst particles. The purification and the evolution of SWCNT material using this procedure are monitored using optical absorption spectroscopy, transmission electron microscopy including electron energy-loss spectroscopy as well as electron diffraction. Furthermore, the method has a sufficiently high yield of about 50% to be applicable for a large-scale purification. PACS 81.05.-t; 81.20.-n; 81.07.-b     

Total Atomic Scattering Factors of 1s^23s ^2S States for Lithium Isoelectronic Sequence

Total atomic scattering factors for the 1s^23s ^2S stages for the lithium isoelectronic sequence from Z = 3 - 10 are calculated by using the full core plus correlation wave function. The influence of electron correlation on total atomic scattering factors is considered sufficiently in our calculation. For the 1s^2 3s ^2S states of the lithium isoelectronic sequence, the general functional behaviour of total atomic scattering factors is analyzed together for each state of the isoelectronic sequence.     

钾原子4S-6S双光子共振的实验研究

利用YAG激光抽运的染料激光器将钾原子由基态 4S双光子共振激发到 6S态 ,研究了钾原子 4S 6S双光子共振三光子电离的电离谱与温度、激光强度的关系 ,发现电离流的强度随着温度的升高而增强 ,当温度在 370℃附近时达到最大值 ,此时温度继续升高电离流强度减弱。在温度不变的情况下 ,电离流强度随着激光能量的增强而增强 ,当激光强度为 4 5× 10 5W /mm2 时到达最大值 ,继续增加激光强度 ,电离流强度趋于饱和。实验中观测到对应于 6S 4P的自发辐射     

CPT原子钟参数设计及其光谱实验研究

通过建立被动型CPT铯原子钟的理论模型,开展CPT信号与铯原子气室特性参量间关系的仿真分析和研究,建立铯原子气室设计及分析方法,得到了被动型CPT铯原子钟最佳设计参数,直径10 mm、长度10 mm、缓冲气体为N₂的圆柱形铯原子气室,最佳工作参数为：工作温度为320 K、气体压强值50 Torr。并经多波长多普勒吸收光谱、CPT信号锁定及频率稳定度测试等实验,验证了理论模型的正确性,为开展高性能芯片级CPT铯原子钟的设计、参数优化提供了一种研究方法。     

A Clear Atomic Example for the Surface Sensitivity of Penning Ionization: He*(23S) + Yb

Using a crossed-beam apparatus with a double hemispherical electron spectrometer, we have studied the spectrum of electrons released in thermal energy ionizing collisions of metastable He*(2³S) atoms with ground state Yb(4f¹⁴ 6s^{2 1}S₀) atoms, thereby providing the first Penning electron spectrum of an atomic target with 4f-electrons. In contrast to the Hel (58.4 nm) and NeI (73.6/74.4 nm) photoelectron spectra of Yb, which show mainly 4f- and 6s-electron emission in about a 5:1 ratio, the He*(2³S) Penning electron spectrum is dominated by 6s-ionization, accompanied by some correlation-induced 6p-emission (8% Yb⁺(4f¹⁴ 6p ²P) formation) and very little 4f-ionization (?2.5%). This astounding result is attributed to the electron exchange mechanism for He*(2³S) ionization and reflects the poor overlap of the target 4f-electron wavefunction with the 1s-hole of He*(2³S), as discussed on the basis of Dirac-Fock wave functions for the Yb orbitals and through calculations of the partial ionization cross sections involving semiempirical complex potentials. The presented case may be regarded as the clearest atomic example for the surface sensitivity of He*(2³S) Penning ionization observed so far.     

Electroweak S and T parameters from a fixed point condition

We consider the standard model without the Higgs boson, where the Goldstone modes are described by a nonlinear sigma model. We study the renormalization group flow of the sigma model coupling f and of the electroweak parameters S and T. The condition that the couplings reach a fixed point at high energy leaves the low energy values of f and T arbitrary (to be determined experimentally) and fixes S to a value compatible with electroweak precision data.     

原子廓线激光多普勒测速仪

论述了用原子滤波器的透射率廓线测量激光多普勒频移的直接检测方法和理论，报道了基于这个方法的一个原理性实验。实验采用二极管泵浦的连续倍频Ｎｄ；ＹＡＧ激光器作为发射器，和一个温控的透射率翼宽为３８０ＭＨＺ的碘滤波器作为多普勒频移检测器件进行了转透速度的测量。     

Atomic structure calculations for F-like tungsten

Energy levels, wavefunction compositions and lifetimes have been computed for all levels of 1s22s22p5, 1s22s2p6,1s22s22p43 s, 1s22s22p43 p, and 1s22s22p43 d configurations in highly charged F-like tungsten ion. The multiconfigurational Dirac–Fock method(MCDF) is adopted to generate the wavefunctions. We have also presented the transition wavelengths,oscillator strengths, transition probabilities, and line strengths for the electric dipole(E1) and magnetic quadrupole(M2)transition from the 1s22s22p5 ground configuration. We have performed parallel calculations with the flexible atomic code(FAC) for comparing the atomic data. The reliability of present data is assessed by comparison with other theoretical and experimental data available in the literature. Good agreement is found between our results and those obtained using different approaches confirm the quality of our results. Additionally, we have predicted some new atomic data for F-like W that were not available so far and may be important for plasma diagnostic analysis in fusion plasma.     

Atomic pseudopotentials for soft X-ray excitations

A new method for determining atomic pseudopotentials from photoemission angular distributions is proposed and applied to the soft X-ray 3p-to-continuum transitions of Ar.