Relativistic Dirac-Fock-Slater orbital binding energies and one-electron transition energies Cu XVI–XIX,Zn XVII–Zn XX,Ag XI–Ag XIX,and Sn XVIII–Sn XXIII

Listed here are the electron orbital energies of the ions Cu XVI to Cu XIX, Zn XVII to Zn XX, Ag XI to Ag XIX, and Sn XVIII to Sn XXIII for different configurations defined by the outermost electron. These values have been computed by the relativistic self-consistent field method. From these configurations the one-electron transition energies in sudden approximation are obtained. Adiabatic transition energies can also be obtained but are not listed here. These tables may be helpful in the identification of transitions in the spectra which are currently being measured in laser-produced plasmas.     

Calculated half-lives and kinetic energies for spontaneous emission of heavy ions from nuclei

The most probable decays by spontaneous emission of heavy ions are listed for nuclides with Z = 47−106 and total half-lives > 1 μsec. Partial half-lives, branching ratios relative to α decay, kinetic energies, and Q values are estimated by using the analytical superasymmetric fission model, a semi-empirical formula for those α-decay lifetimes which have not been measured, and the new Wapstra-Audi mass tables. Numerous “stable” nuclides with Z > 40 are found to be metastable with respect to the new decay modes. The current experimental status is briefly reviewed.     

Ionization energies of tungsten ions: W through W

A semi-empirical method is used to determine ionization energies of multiply charged tungsten ions, W²⁺ through W⁷¹⁺. The method is based on Hartree-Fock calculations of electron binding energies scaled according to experimental results. The relative uncertainties vary from 1.7% for W²⁺ to 0.015% for W⁷¹⁺. The resulting values are tabulated with results of experiments and precise theoretical calculations in a list of ionization energies for tungsten in all stages of ionization, W through W⁷³⁺.     

Calculated fission barriers,ground-state masses,and particle separation energies for nuclei with 76 ≤ Z ≤ 100 and 140 ≤ N ≤ 184

We calculate fission barriers and ground-state masses for 1125 nuclei with 76 ≤ Z ≤ 100 and 140 ≤ N ≤ 184. We use the macroscopic-microscopic method to calculate the energy as a function of elongation, necking, mass-asymmetric, and axially asymmetric shape coordinates. For the macroscopic model we use the droplet model with a 1973 set of parameters. The microscopic corrections are calculated by use of the modified oscillator model. The results are summarized in two tables. The first table gives, for each nucleus, the heights relative to the ground state of the saddle points and minima of the fission barriers and the corresponding values of the shape coordinates. The second table gives the ground-state mass excess, the maximum barrier height, neutron and proton separation energies, and alpha and beta Q-values.     

Tables for plane-wave Born-approximation calculations of K- and L-shell ionization by protons

Tables are presented in universal form for the calculation of plane-wave Born cross sections for proton-impact ionization of the K-shell and of individual L-subshells. The reason for these new calculations was twofold: First, these tables cover a wider range of proton energies and target binding energies than the original tables of Khandelwal et al., so that corrections for increased binding energy, Coulomb deflection etc. can be taken into account. Second, the table values have been calculated with the exact physical limits of integration given by energy and momentum conservation. This leads to lower cross-section values than in the original tables for low proton energies.     

Semiempirical Auger-electron energies for elements 10 ≤ Z ≤ 100

Auger-electron energies are calculated for a wide range of transition processes in elemental systems by means of a general semiempirical method developed within an intermediate-coupling framework. Experimental electron subshell binding-energy data are combined with Slater integral values, an adiabatic relaxation correction term, and, where appropriate, a solid-state correction term. The approach uses data derived from atomic Hartree-Fock calculations and does not require any fitting to experimental Auger energies. The limitation on accuracy is closely related to the reliability of available electron binding-energy data. For systems where such values are known to high accuracy, agreement between experimental and calculated Auger-electron values is generally within 1–2 eV with the maximum discrepancies near 5 eV. However, when the uncertainties in the binding energies used are larger, such uncertainties are correspondingly associated with the Auger-electron energy predictions. The values presented in these tables may be readily modified if superior binding energies become available. Furthermore, with suitable binding-energy data the tables may be adapted to predict Auger-energy values for the vapor phase as well as for the solid phase of the elemental system. With the exception of the elements Ne, Cl, Ar, Br, Kr, Xe, and Rn the tabulated values are for solid systems and are referenced to the Fermi level.     

铀部件质量属性测量中的信噪比初步分析

利用蒙特卡罗程序对252Cf快电离室诱发不同质量金属铀部件的中子输运过程进行了模拟,获得屏蔽与直穿两种实验布局条件下252Cf快电离室与探测器之间的中子时间关联符合计数,初步评估测量过程中的信噪比,作为实验前端布局的重要依据。结果表明,两种布局下的信噪比均与铀部件质量成正比,直穿布局下的信噪比较高。     

Dirac-Fock-Slater calculations for the elements Z = 100, fermium,to Z = 173

Listed here for the elements Z = 100, fermium, to Z = 173 are energy eigenvalues and total energies found from relativistic Dirac-Fock-Slater calculations. The effect of high ionization on the energy eigenvalues is presented for two examples. The use of these tables in connection with the energy levels of superheavy elements and molecular orbital (MO) x-ray transitions in superheavy quasiatoms, is discussed. In addition, a brief comparison between the results of the Dirac-Fock-Slater and Dirac-Fock calculations is given.     

Interaction of 960 MeV/nucleon- 238U ions with light target atoms of CR-39 polycarbonate

CR-39 plastic track detectors have been employed both as the target and as the detector to study the interaction of 960 MeV/nucleon-²³⁸U ions with light target atoms (hydrogen, carbon, and oxygen), the constituents of CR-39. The experimental value of the mean free path (mfp) for the relativistic uranium ions has been obtained and compared with the value computed theoretically. The range of the uranium ions has been found to be 6.5 cm in the composite medium of CR-39 track detectors. The average multiplicity due to fission of the uranium projectiles in CR-39 track detecting medium has been found to be 2.1, which indicates that binary fission is the most common mode of interaction.     

活动态U、Mo测量在SHTL地区砂岩型铀矿勘查中的应用

元素活动态测量是一种深穿透地球化学找矿方法。为了在北方砂岩型铀矿找矿中减小钻探的盲目性,实现快速评价,作者在二连盆地SHTL地区开展了壤中活动态U、Mo测量,以寻找砂岩型铀矿。选取U、Mo活动态中的黏土吸附态作为测量对象,在测区内共圈定壤中黏土吸附态U异常7 个、Mo异常5个。通过U、Mo异常评价并结合地质条件,预测了3个远景地段;经钻探验证发现了铀矿化,表明了活动态U、Mo测量寻找砂岩型铀矿床的有效性。建议在远景地段内进一步进行钻孔揭露。     

Theoretical cross sections of Bi,Th, U and U on deuteron-induced reactions

There are many application fields for fast neutrons. The main application fields of the fast neutrons are accelerator-driven sub-critical systems (ADS) and fusion–fission (hybrid) reactor systems for fission energy production. Thorium (Th) and uranium (U) are nuclear fuels in fusion–fission (hybrid) reactor systems and bismuth (Bi) is also the target nucleus in the ADS reactor systems. In this study, neutron production cross sections produced by (d, xn) reactions for spallation targets such as ²⁰⁹Bi, ²³²Th, ²³⁵U and ²³⁸U have been investigated. New evaluated hybrid model and geometry dependent hybrid model have been used to calculate the pre-equilibrium neutron production cross sections. For the reaction equilibrium component, Weisskopf–Ewing model calculations have been preferred. The obtained results have been discussed and compared with the available experimental data and found in agreement with each other.     

Energy loss of energetic Ar, Kr, Au and U ions in mylar, aluminum and isobutane

The BigSol Superconducting Solenoid Beam Line at the Texas A&M Superconducting Cyclotron has been used to measure energy losses of ⁴⁰Ar, ⁸⁴Kr, ¹⁹⁷Au and ²³⁸U ions in mylar, aluminum and isobutane at energies ranging from the Bragg peak up to several MeV/nucleon. The experimental data are compared with predictions from the SRIM code. In general experimental data for ⁴⁰Ar and ⁸⁴Kr are in agreement with model predictions whereas differences on the order of 10% are evidenced in some cases for ¹⁹⁷Au and ²³⁸U ions especially at and around the Bragg peak energies.     

超高真空脉冲激光沉积Au、U单层膜及Au/U/Au复合膜研究

采用超高真空脉冲激光沉积（PLD）方法,在单晶Si基底表面制备了单层Au、单层U薄膜和Au/U/Au复合薄膜,应用SEM、白光干涉轮廓分析和AES分析,研究了靶基距、基片温度和激光能量对薄膜形貌、成分的影响。目前的实验结果显示,PLD所制备的Au、U薄膜表面有μm级以下粒径的液滴产生,在液滴较少位置,薄膜表面粗糙度R_a小于1 nm,在包含大液滴位置,R_a不超过15 nm。在相同沉积条件下,U薄膜表面液滴数量大于Au薄膜。优化单层薄膜沉积工艺后制备的Au/U/Au复合膜厚度约为195 nm,均方根粗糙度R_q在0.3～1.5 nm之间。AES分析显示,Au/U/Au复合膜中强化学活性的铀呈金属状态,复合膜中的氧含量低于5%（原子百分数）,表层Au薄膜对U薄膜起到了良好的防氧化作用。在沉积工艺中,通过减小激光功率、增大靶基距并适当升高基片温度,可减少液滴的数量及粒径。     

Energetics of intrinsic point defects in uranium dioxide from electronic-structure calculations

The stability range of intrinsic point defects in uranium dioxide is determined as a function of temperature, oxygen partial pressure, and non-stoichiometry. The computational approach integrates high accuracy ab initio electronic-structure calculations and thermodynamic analysis supported by experimental data. In particular, the density functional theory calculations are performed at the level of the spin polarized, generalized gradient approximation and includes the Hubbard U term; as a result they predict the correct anti-ferromagnetic insulating ground state of uranium oxide. The thermodynamic calculations enable the effects of system temperature and partial pressure of oxygen on defect formation energy to be determined. The predicted equilibrium properties and defect formation energies for neutral defect complexes match trends in the experimental literature quite well. In contrast, the predicted values for charged complexes are lower than the measured values. The calculations predict that the formation of oxygen interstitials becomes increasingly difficult as higher temperatures and reducing conditions are approached.     

Nucleogenic Cl, U and Pu in uranium ores

The nucleogenic isotopes ³⁶Cl, ²³⁶U and ²³⁹Pu are produced naturally in subsurface environments via neutron capture of thermal and epithermal neutrons. Concentrations are, however, very low and accelerator mass spectrometry (AMS) is required for quantitative measurements. A particular challenge is presented by the measurement of ²³⁶U/²³⁸U ratios down to the level of 10⁻¹³ that is expected from rocks with low uranium concentration. Here, we present the AMS methodology that has been developed at the ANU for measuring ²³⁶U/²³⁸U ratios at this level. The more established methodologies for ³⁶Cl and ²³⁹Pu measurements are also summarised. These capabilities are then used to characterize the ³⁶Cl, ²³⁶U and ²³⁹Pu concentrations in a range of uranium ores. A simple model of the neutron production and capture processes in subsurface environments has been developed and is presented. It is shown that nucleogenic ³⁶Cl, ²³⁶U and ²³⁹Pu can be used to determine both thermal and epithermal neutron fluxes in subsurface environments. Potential applications include uranium exploration and monitoring of the environmental impact of uranium mining.     

Intermediate-coupling collision strengths for P−P and P−D transitions produced by electron impact on highly charged He-like ions

Intermediate-coupling collision strengths have been calculated by a Coulomb-Born-Exchange method for all fine-structure transitions between states of the 1s2p configuration and those of the 1snp and 1snd configurations with n = 3, 4, and 5 produced by electron impact on He-like ions with nuclear charge number Z in the range 8 ≤ Z ≤ 50. For each transition results are given for impact electron energies equal to 1.0, 1.2, 1.5, 1.9, 2.5, and 4.0 times threshold. Transition energies are provided for use in converting the impact electron energies to energies in rydbergs.     

Isoelectronic sequence fits to configuration-averaged photoionization cross sections and ionization energies

Hartree-Fock wave functions have been used to calculate configuration-averaged photonization cross sections and ionization energies for orbitals 1s ⩽ nl ⩽ 5g in He-like through Al-like isoelectronic sequences. The photoionization cross sections have been fitted as a function of the nuclear charge, Z, and photon energy, X, in threshold units, with average error of less than 10%. The ionization energies have been fitted as a function of Z with errors of less than 0.5%.     

Stopping power measurements for O, F and Si ions in Mylar by a transmission technique

Electronic energy loss of charged particles in materials is a fundamental process responsible for the unique response of materials in applications of advanced nuclear power, radiation detectors and advanced processing of electronic devices. In this study, stopping powers of ¹⁶O, ¹⁹F and ²⁸Si heavy ions crossing thin Mylar foils have been determined in transmission geometry. The energy loss was measured over a continuous range of energies from 1.6 to 5.5 MeV/n (MeV per nucleon) using the data that was tagged by a surface barrier detector (SBD) with and without stopping foils. We have compared the obtained stopping values to those predicted by SRIM-2008 computer code, ICRU-73 stopping data tables and MSTAR calculations. The effective charge values of these heavy ions have been also deduced from the experimental set of data.     

Determination of uranium content in Th, U mixed oxides using EDXRF

An energy dispersive X-ray fluorescence (EDXRF) technique has been developed for the determination of U content in the range 2-80% in mixed oxides of thorium and uranium. The experimental parameters for XRF measurements were optimized using 1 cm diameter pellets made from 1:1 mixture of thorium-uranium mixed oxide standards and cellulose. Calibration plots were established using both L_α as well as L_β peaks of uranium. The reproducibility of the determination was evaluated to be better than 3% for L_α peak, while for L_β peak, it was better than 4%. The measured values of the uranium concentration in the synthetic samples were found to be in good agreement with the added values. Simultaneously Th was also determined using its L_α peak. The present method will be useful for fast routine measurements of mixed oxide samples of Th and U, without the need for dissolution.     

Interfacial energies between uraniumdioxide and liquid metals

Interfaciai energies between solid uranium dioxide and liquid metals have been investigated for a number of systems. It was found, that at the metal melting point (1) the interfacial energies become approximately identical for all metals (γUO₂-liquid metals ≈ 1.676 ± 0.142 J/m²) with respect to an engineering approach, and (2) the respective contact angles (φ_s > 90°) point out no wettability. Linear temperature functions of interfacial energies in UO₂ -liquid metal systems have been derived. By appropriate extrapolation procedures it is possible to estimate temperature coefficients of interfacial energies for not yet measured solid UO₂ -liquid metal systems.