Calculations on polarization properties of alkali metal atoms using Dirac–Fock plus core polarization method

A semi-empirical atomic structure model method is developed in the framework of a relativistic case. This method starts from Dirac-Fock calculations using B-spline basis set. The core-valence electron correction is then treated in a semiempirical core polarization potential. As an application, the polarization properties of alkali metal atoms, including the static polarizabilities and long-range two-body dispersion coefficients, have been calculated. Our results are in good agreement with the results obtained from ab initio relativistic many-body perturbation method and the available experimental measurements.     

MBA接枝聚丙烯微孔膜的亲水改性研究

运用表面吸附法使聚丙烯微孔膜表面覆盖上引发剂,然后浸入氮氮亚甲基双丙烯酰胺(MBA)水溶液在一定温度下进行接枝反应。研究了引发剂用量,单体浓度,反应时间与温度对接枝率的影响,并用红外、扫描电镜对聚丙烯膜接枝前后的微孔膜进行了表征。同时对膜的亲水性和水通量进行了测试,发现其亲水性能有了极大的提高,其中接枝改性后接触角与未接枝的相比降低了90°以上,吸水率最多提高了12%,但是水通量有所下降。还对改性微孔膜的抗污染性能进行了探究。     

高准确度的钙离子光频标

近年来,冷原子技术和激光技术促进了高精度光频标的发展,有望在建立时间基准、推动基础研究和满足国家需求等方面发挥重要的作用.本文介绍了中国科学院武汉物理与数学研究所近年来在高准确度钙离子(~(40)Ca~+)光频标研究方面的进展:采用新的ULE腔系统,实现了729 nm钟跃迁激光器1—100 s的频率稳定度均优于2×10~(-15),通过对外场和环境效应的控制及克服,特别是囚禁离子运动效应的抑制,获得单个钙离子光频标的不确定度优于5.5×10~(-17);通过两台光频标的比对,测得20000 s的稳定度也进入10~(-17)量级;基于高精度钙离子光频标平台,进行了相关精密测量的工作,包括:基于全球定位系统的超高精度远程光频绝对值测量方案,第二次测量了钙离子的光频跃迁绝对值,该测量结果再次被国际时间频率咨询委员会采纳,更新了钙离子的频率推荐值;精确测量了钙离子的钟跃迁魔幻波长,由此提出新型的全光囚禁离子光频标的方法;精密测量了钙离子的亚稳态寿命等参数.以上工作推动了基于冷原子的精密测量工作.     

Theoretical investigation on forbidden transition properties of fine-structure splitting in ~2D state for K-like ions with 26≤Z≤36

Excitation energies, magnetic dipole, and electric quadrupole transition probabilities of the 3d~2 D_(3/2)–3d~2D_(5/2) transition in the potassium-like(K-like) sequence with 26≤Z≤36 are investigated by using the multi-configuration Dirac–Hartree–Fock(MCDHF) method. The contributions of the electron correlations, Breit interaction, and the leading-order quantum electrodynamic(QED) effects on the transition properties are analyzed. The present results are interested in the laboratory tokamak and the astronomical observations. Furthermore, the feasibility of these ions for the highly charged ion(HCI) clocks is discussed. Considering the wavelength of lasers and manipulation process of the atomic clocks, Cu~(10+)and Zn~(11+)are recommended as promising candidates with achievable quality factors at the 10~(15) level.     

Dynamic polarizabilities of the clock states of Al+

The dynamic polarizabilities of ${\rm 3s}^2\,^1{\rm S}_0$ and ${\rm 3s}{\rm 3p}\,^3{\rm P}_0^{\rm o}$ states of Al$^+$ are calculated using the hybrid configuration interaction and many-body perturbation theory method, and multiconfiguration Dirac-Hartree-Fock method in this work. Five ultraviolet magic wavelengths for the Al$^+$ clock transition ${\rm 3s}^2\,^1{\rm S}_0$-${\rm 3s3p}\,^3{\rm P}_0^{\rm o}$ are predicted. Although the suitable lasers are not available presently, the potential precision measurement on these magic wavelengths for the Al$^+$ clock transition would be used to extract the ratios of several certain transition matrix elements with high accuracy, and then help to improve the precision and reliability of the estimate of the BBR shift of the Al$^+$ clock transition. The differential dynamic polarizabilities at certain wavelengths are evaluated, which are useful to assess the ac Stark shift of the Al$^+$ clock transition frequency and helpful in the clock experiments to suppress the ac Stark shift of the clock transition as possible as it can.     

Magic wavelengths for the 7s_(1/2)6d_(3/2,5/2)transitions in Ra~+

The dynamic polarizabilities of the 7s and 6d states of Ra~+are calculated using a relativistic core polarization potential method.The magic wavelengths of the 7s_(1/2)–6d_(3/2,5/2)transitions are identified.Comparing to the common radiofrequency(RF) ion traps,using the laser field at the magic wavelength to trap the ion could suppress the frequency uncertainty caused by the micromotion of the ion,and would not affect the transition frequency measurements.The heating rates of the ion and the powers of the laser for the ion trapping are estimated,which would benefit the possible precision measurements based on all-optical trapped Ra+.     

蒙特卡罗法模拟新型扫描电镜的工作原理

根据新型分析扫描电子显微镜的工作原理及载能电子束和固体相互作用原理,利用蒙特卡罗方法模拟入射电子和靶物质的相互作用过程,编制了蒙特卡罗模拟计算程序,获得了对应不同电镜工作参数的入射电子背散射率.     

First principles study on the charge density and the bulk modulus of the transition metals and their carbides and nitrides

A first principles study of the electronic properties and bulk modulus （B0） of the fcc and bcc transition metals, transition metal carbides and nitrides is presented. The calculations were performed by plane-wave pseudopotential method in the framework of the density functional theory with local density approximation. The density of states and the valence charge densities of these solids are plotted. The results show that B0 does not vary monotonically when the number of the valence d electrons increases. B0 reaches a maximum and then decreases for each of the four sorts of solids. It is related to the occupation of the bonding and anti-bonding states in the solid. The value of the valence charge density at the midpoint between the two nearest metal atoms tends to be proportional to B0.     

TiN／VN超晶格薄膜的切变弹性模量的计算

采用赝势方法计算TiN/VN超晶格薄膜的能带结构，并计算了TiN/VN超晶格原胞的总能量，进而得到了该材料的切变弹性模量C44随超晶格周期的变化关系，C44出现最大值时所对应的周期与实验值基本一致。     

Theoretical study of the hyperfine interaction constants,Landé g-factors,and electric quadrupole moments for the low-lying states of the 61Niq+(q=11,12,14,and 15) ions

Highly charged nickel ions have been suggested as candidates for the ultra-precise optical clock, meanwhile the relevant experiment has been carried out. In the framework of the multiconfiguration Dirac–Hartree–Fock(MCDHF)method, we calculated the hyperfine interaction constants, the Landég-factors, and the electric quadrupole moments for the low-lying states in the 61Ni11+,61Ni12+,61Ni14+, and61Ni15+ ions. These states are clock states of the selected clock transitions in highly charged nickel ions(see Fig. 1). Based on discussing the effects of the electron correlations, the Breit interaction, and quantum electrodynamics(QED) effect on these physical quantities, reasonable uncertainties were obtained for our calculated results. In addition, the electric quadrupole frequency shifts and the Zeeman frequency shifts of the clock transitions concerned were analyzed.