An effective method to calculate the electron impact excitation cross sections of helium from ground state to a final channel in the whole energy region

The electron impact excitation(EIE) cross sections of an atom/ion in the whole energy region are needed in many research fields, such as astrophysics studies, inertial confinement fusion researches and so on. In the present work, an effective method to calculate the EIE cross sections of an atom/ion in the whole energy region is presented. We use the EIE cross sections of helium as an illustration example. The optical forbidden 1^(1)S–n^(1)S(n = 2–4) and optical allowed 1^(1)S–n^(1)P(n = 2–4) excitation cross sections are calculated in the whole energy region using the scheme that combines the partial wave R-matrix method and the first Born approximation. The calculated cross sections are in good agreement with the available experimental measurements. Based on these accurate cross sections of our calculation, we find that the ratios between the accurate cross sections and Born cross sections are nearly the same for different excitation final states in the same channel. According to this interesting property, a universal correction function is proposed and given to calculate the accurate EIE cross sections with the same computational efforts of the widely used Born cross sections,which should be very useful in the related application fields. The datasets presented in this paper are openly available at https://www.doi.org/10.57760/sciencedb.j00113.00142.

SIMT守时氢原子钟频率漂移对稳定度影响

采用阿伦方差定量分析SIMT守时氢原子钟不同采样间隔的频率稳定性能,采用线性拟合的方式估计氢原子钟频率漂移率,通过比较阿伦方差和哈达玛方差分析频率漂移对频率稳定度影响。并分析一年半时间内,氢原子钟每月的日频率漂移率变化情况,分析主钟频率漂移变化对守时系统稳定性的影响。

离化态原子基态电子结构特征与轨道竞争规律

离化态原子广泛存在于等离子体物质中,其相关性质是天体物理、受控核聚变等前沿科学研究领域的重要基础.基于独立电子近似,本文系统研究了扩展周期表元素(2 Z 119)所有中性和离化态原子的基态电子结构.基于设计的原子轨道竞争图,系统总结了各周期元素轨道竞争的规律,并结合离化态原子的局域自洽势阐明了其轨道竞争(即轨道塌陷)的机制;在此基础上,说明了部分元素性质与轨道竞争的关系.利用本文研究得到的离化态原子基态电子结构,可建立更精密计算相关原子的能级结构、跃迁几率等物理量之基础,从而满足高功率自由电子激光实验分析、原子核质量精密测量等前沿研究的需求.

Interesting Features of Ionization Potentials for Elements(Z≤119)along the Periodic Table

The ionization potential （IP） is a basic property of an atom, which has many applications such as in element analysis. With the Dirac-Slater methods （i.e., mean field theory）, IPs of all occupied orbitals for elements with atomic number （Z ≤ 119） are calculated conveniently and systematically. Compared with available experimental measurements, the theoretical accuracies of IPs for various occupied orbitals are ascertained. The map of the inner orbital IPs with Mood accuracies should be useful to select x-ray energies for element analysis. Based on systematic variations of the first IPs for the outermost orbitals in good agreement with experimental values as well as other IPs, mechanisms of electronic configurations of all atomic elements （Z ≤ 119） along the periodic table are elucidated. It is interesting to note that there exist some deficiencies of the intermediate orbital IPs, which are due to electron correlations and should be treated beyond the mean field theory.

Electron impact excitation of helium atom

A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.

JJG488-2018《瞬时日差测量仪检定规程》解读

为适应计时器测量技术发展，拓展2008版规程测量范围和适用范围，清晰基本概念，国质检量函[2015]146号“质检总局关于下达2015年国家计量技术法规制修订计划的通知”，批准《瞬时日差测量仪》国家计量检定规程的修订工作主要由上海市计量测试技术研究院和广东省计量科学研究院承担。本规程于2018年2月27日发布，同年8月27日实施。

钟组守时性能分析

针对原子钟的技术指标,对比分析了不同钟组配置的时标性能。根据典型原子钟的技术指标和实际运行情况对氢钟和铯钟钟差数据进行仿真,应用ALGOS算法计算了铯钟组、氢钟组、氢铯联合钟组的原子时标,从时间偏差、时间稳定度、频率偏差、频率稳定度四个方面考察了钟组时标性能。结果表明,180台仿真铯钟的守时天频率稳定度相当于1台氢钟的守时天频率稳定度;由于铯钟频率稳定度与氢钟相差较大,原子时计算过程中,铯钟权重远低于氢钟,对原子时的贡献有限;氢钟占比高的钟组,时标稳定性较好,溯源状态下时间偏差和频率偏差也较小。时标稳定性好的钟组在守时状态下的时间保持能力也更好。