Testing the reliability of non-LTE spectroscopic models for complex ions

Collisional-radiative atomic models are widely used to help diagnose experimental plasma conditions through fitting and interpreting measured spectra. Here we present the results of a code comparison in which a variety of models determined plasma temperatures and densities by finding the best fit to an experimental L-shell Kr spectrum from a well characterized, but not benchmarked, laser plasma. While variations in diagnostic strategies and qualities of fit were significant, the results generally confirmed the typically quoted uncertainties for such diagnostics of ±20% in electron temperature and factors of about two in density. The comparison also highlighted some model features important for spectroscopic diagnostics: fine structure was required to match line positions and relative intensities within each charge state and for density diagnostics based on emission from metastable states; an extensive configuration set was required to fit the wings of satellite features and to reliably diagnose the temperature through the inferred charge state distribution; and the inclusion of self-consistent opacity effects was an important factor in the quality of the fit.     

The effect of the relativistic Hartree-Fock-Roothaan momentum distribution in the binary encounter approximation for inner shell ionization

K- and L-shell ionization cross sections of gold due to impact of proton and alpha particles have been calculated in the binary encounter approximation incorporating the effects of Coulomb deflection of the projectile, of increase in binding of the target electron, and of polarization and relativity. Relativistic Hartree-Fock-Roothaan (RHFR) momentum distributions for the target electron along with an approximate relativistic correction to the collision dynamics have been used in the present calculations. A comparison with the corresponding calculations using non-relativistic Hartree-Fock-Roothaan wave functions, experimental results and other available calculations is presented.     

Nd L-shell x-ray emission induced by light ions

The L-shell x-ray of Nd has been obtained for 300-600 keV He²⁺ ions impacting, and compared with that produced by H⁺ and H₂⁺ ions. The threshold of projectile kinetic energy for L-shell ionization of Nd is crudely verified in the energy region of about 300-400 keV. It is found that the energy of the distinct L-subshell x-rays has a blue shift. The relative intensity ratios of Lβ_{1, 3, 4} and Lβ_{2, 15} to Lα_{1, 2} x-ray are enlarged compared to the atomic data, and they decrease with the increase of the incident energy, and increase with increasing the effective nuclear charge of the incident ions. That is interpreted by the multiple ionization of outer-shells induced by light ions.     

用类Ne离子L带特征线诊断等离子体特性初步实验研究

本文描述在X光激光实验中用平晶谱仪测量类Ne锗离子L带线谱,首次借助于碰撞辐射模型,用L带特征线的强度所确定等离子体电子密度和温度。并用平晶谱仪配条纹相机测量等离子体的时间特性。     

L—shell absorption measurement and simulation of x—ray—heated constrained material

Using the newly-designed multi-layered target, we obtain a homogeneous Al sample plasma at high density, low electron temperature, and in near local thermodynamic equilibrium. L-shell resonance absorption lines of Li-like and Be-like ions, as well as satellites are clearly observed. Transition arrays such as 2s－3p, 2s²－2s3p and 2s2p－2p3p are identified. We present the calculation method based on the unresolved transition array model, and we compare the measured transmission spectrum with the calculated results. The electron temperature of the constrained sample plasma is determined to be 34eV with a variation of ±2eV.     

Ionization for Hf- and W-L-shell by electron impact

Electron-induced Hf-, W-L-shell partial, total production cross sections, mean ionization cross sections and Hf-L_3-shell ionization cross sections (at two energies) have been measured as functions of electron energies (from near threshold to 36keV). The influence of electrons reflected from the backing of the thin targets on measured results was corrected using a model to relate to the electron transport process. The mean paths of electron multi-scattered in the target itself (including forward and backward scattering) were calculated by means of Monte Carlo program (EGS4) and they were used to correct measured results. A comparison with both theoretical predictions was given.     

MEASUREMENT OF L-SHELL IONIZATION CROSS SECTIONS FOR NIOBIUM BY ELECTRON IMPACT

L-shell ionization cross sections of Nb by electron impact in the energy range from 3 to 40 keV have been determined with a Si(Li) X-ray detector. Influence of reflected electrons from backing on the measurement was corrected using an electron transport model. The experimental results are compared with theoretical calculations of Gryzinski and McGuire.     

Density functional theory calculation of 2p core-electron binding energies of Si,P, S,Cl, and Ar in gas-phase molecules

Density functional theory (DFT) calculations have been performed on the gas-phase 2p core-electron binding energies (CEBEs) of Si, P, S, Cl, and Ar in 145 cases using the following procedure: ΔE_KS (scalar-ZORA + E_xc)/TZP//HF/6-31G(d). ΔE_KS is the difference in the total Kohn–Sham energies of the 2p-ionized cation and the neutral parent molecule calculated by DFT using different exchange-correlation functionals E_xc with triple-zeta polarized basis set, at molecular geometry optimized by HF/6-31G(d), and relativistic effects have been estimated by scalar zeroth-order regular approximation. Among the 26 functionals tested, the form of E_xc giving the best overall performance was found to be the combination of OPTX exchange and LYP correlation functionals. For that functional, the average absolute deviation (AAD) of the 145 calculated CEBEs from experiment is 0.26 eV. There are seven other exchange-correlation functionals that led to AADs of less than 0.30 eV. Some functionals give lower AADs than E_xc = OPTX-LYP for some individual elements. In the case of Si, for example, the combination of either mPW91-PBE or Becke88-Perdew86 led to an AAD of only 0.10 eV for 56 silicon-containing molecules. Another example is the case of the argon atom, for which the choice of E_xc = OPTX-Perdew86 yields a value for CEBE equal to the experimental value.     

线状锗等离子体空间分布特性实验研究

在电子碰撞激发类Ne锗X光激光实验的基础上,对线状等离子体空间分布特性进行定量测量和分析。首次给出了线状等离子体分布尺度,同时也研究了不同的激光参数和靶结构对等离子体状态的影响。     

正电子碰撞Ag，In，Sn原子L壳层电离截面的理论计算

在David Botz分析模型的基础上,综合考虑正电子及电子碰撞电离的库仑效应和电子交换效应,引入离子效应和相对论效应修正因子,计算了Ag,In,Sn原子的L壳层电离截面.计算结果表明,引入了修正因子的计算结果明显优于平面波波恩近似和扭曲波波恩近似的计算结果,并和最近文献的实验值符合得较好.其计算结果可为激光等离子体模拟提供准确参数.