Mαβ X-ray production cross sections of Pb and Bi by 9-40 keV electron impactMαβ X-ray production cross sections of Pb and Bi by 9-40 keV electron impact

The experimental data of Ma/3 X-ray production cross sections for Pb and Bi by 9-40 keV electron impact have been given. Thin films with thick carbon substrates are used in the experiment. The effects of target structure on the Ma/3 X-ray production cross sections are corrected by using the Monte Carlo method. The corrected experimental data are compared with calculated cross sections in terms of the distorted-wave Born approximation （DWBA） theory. The measured Ma/3 X-ray production cross sections for Pb and Bi are lower than the DWBA calculations. The atomic relaxation parameters used in comparing the DWBA values with experimental results affect the degree of difference.     

L-Shell X-Ray Production Cross Sections of Ta and Tm by Electron Impact near the Threshold Region

We present experimental measurements of L-shell production cross sections Lα, Lβ and Lγ for tantalum and thulium by electron impact at incident electron energies from about one to three times the threshold energy. From the experimental data, the total production cross section and mean ionization cross section are deduced. The influence of electrons reflected from the substrate is corrected by the electron transport bipartition model. Tile measured cross sections are compared with the theoretical predictions.     

Cross Section of Heavy Ion Reaction （14.5 MeV/u） ^132Xe ＋ Bi

We investigate the cross section of the heavy ion reaction （14.5 MeV/u） ^132Xe ＋ Bi by using a CR-39 plastic track detector. The target-detector assembly is exposed at UNILAC beam facility of GSI, Germany. After etching under appropriate etching conditions, the detector is scanned for multipronged events produced as a result of interactions of projectile ions with target atoms. The elastic events are separated from binary events and used for the determination of the quarter-point angle. The quarter-point angle obtained is used to determine the total reaction cross section. The total experimental reaction cross section is determined by using statistics of inelastic events of two-pronged and higher multiplicity events. The experimental reaction cross sections determined by using elastic and inelastic data observed in the reaction under study are found to be in good agreement with the theoretically calculated value of reaction cross section using a sharp cutoff model.     

Entrance Channel Dependence of Production Cross Sections of Superheavy Nuclei in Cold Fusion Reactions

Production cross sections of superheavy nuclei Rf and Hs for asymmetric and nearly symmetric projectile-target combinations are systematically studied within the framework of the dinuclear system model. The calculated results show that the production cross sections are strongly dependent on the symmetry of reaction systems. The obtained results are in good agreement with the available experimental data for asymmetric reaction systems.For nearly symmetric systems, the model gives opposite results with coupled channel model in which surface vibration and nucleon transfer are included.     

L-Shell X-Ray Production Cross Sections of Au and Ir Atoms by Electron Impact near the Threshold Region

L-shell production cross sections Lα, Lβ and Lγ for Au and Ir atoms have been measured by electron impact at incident electron energies of about one to three times of the threshold energy. The total production cross section and mean ionization cross section were obtained from the experimental results and by using mean fluorescence yield, respectively. The influence of electrons reflected from the substrate and multiple electron scattering inside the target have been corrected. The experimental results are compared with the existing measured results and the theoretical predictions.     

Diffractive Scattering Factorization from J/ψ and γ Associated Production in HERA ep Collisions

Using three sets of Pomeron structure functions,the cross sections of J/ψ and γ associated production via resolved photon and proton diffractive scatting in ep collision are investigated.It is found that the cross sections calculated with various gluon distribution functions of Pomeron are different.The discrepancy is about 1.8 times for differential cross sections and 1.7 times for total cross sections.The experimental studies of the process could give valuable insight in the diffractive production mechanism and test the color-octet mechanism for heavy quarkonium production in a new environment.     

The fragmentation of 20Ne at 400 A MeV

The total charge-changing cross sections and partial cross sections for the production of projectile fragments are measured in the interactions of 400 A MeV ²⁰Ne with aluminum, carbon and polyethylene targets sandwiched with CR-39 plastic nuclear track detectors. The measured total charge-changing cross sections are compared with the predictions using the Bradt-Peters semi-empirical formula, and the NUCFRAG2 and PHITS models. It is shown that the measured experimental results are in good agreement with the theoretical model prediction and other experimental results, and it can be clearly seen that the partial cross sections for fragment production show obvious odd-even effects.     

Post-collision interactions and the polarization effect in （e, 2e） collisions of helium

A modified distorted-wave Born approximation (DWBA) method is used to calculate the triple differential cross sections (TDCSs) in a coplanar asymmetric geometry for the electron impact single ionization of a He (1s2) atom at intermediate and lower energies. The post-collision interaction and the polarization effect in (e, 2e) collisions of helium are considered in the calculations. The polarization potentials from the damping method and density functional theory (DFT) are compared. Theoretical results are compared with the recent experimental data.     

Differential and Integral Cross Sections for Electron Impact Excitation of Lithium

The differential and integral cross sections for electron impact excitation of lithium from the ground state 1s22s to excited states 1s22p, 1s23l （l=s, p, d） and 1s24l （l=s, p, d, f）at incident energies ranging from 5 eV to 25 eV are calculated by using a full relativistic distorted wave method. The target state wavefunctions are calculated by using the Grasp92 code. The continuum orbitals are computed in the distorted-wave approximation, in which the direct and exchange potentials among all the electrons are included. A part of the cross sections are compared with the available experimental data and with the previous theoretical values. It is found that, for the integral cross sections, the present calculations are in good agreement with the time-independent distorted wave method calculation, for differential cross sections, our results agree with the experimental data very well.     

Diffractive Scattering Factorization from J/ψ and γ Associated Production in HERA ep Collisions

Using three sets of Pomeron structure functions, the cross sections of J/ψ and γ associated productionvia resolved photon and proton diffractive scatting in ep collision are investigated. It is found that the cross sectionscalculated with various gluon distribution functions of Pomeron are different. The discrepancy is about 1.8 times fordifferential cross sections and 1.7 times for total cross sections. The experimental studies of the process could give valuableinsight in the diffractive production mechanism and test the color-octet mechanism for heavy quarkonium production ina new environment.     

L-Shell X-Ray Yields and Production Cross Sections of Zr and Mo Bombarded by Slow Highly Charged Ar16+ Ions

The L-shell x-ray yields of Zr and Mo bombarded by slow Ar16＋ ions are measured. The energy of the Ar^16＋ ions ranges from about 150 keV to 350 keV. The L-shell x-ray production cross sections of Zr and Mo are extracted from these yields data. The explanation of these experimental results is in the framework of the adiabatic direct- ionization and the binding energy modified BEA approximation. We consider, in the slow asymmetric collisions such as Ar and Mo/Zr, the transient united atoms （UA） are formed during the ion-surface interaction and the direct-ionization is the main mechanism for the inner-shell vacancy production. Generally, the theoretical results are in good agreement with the experimental data.     

Nonradiative charge transfer in collisions of protons with rubidium atoms

The nonradiative charge-transfer cross sections for protons colliding with Rb(5s) atoms are calculated by using the quantum-mechanical molecularorbital close-coupling method in an energy range of 10 3 keV-10 keV.The total and state-selective charge-transfer cross sections are in good agreement with the experimental data in the relatively low energy region.The importance of rotational coupling for chargetransfer process is stressed.Compared with the radiative charge-transfer process,nonradiative charge transfer is a dominant mechanism at energies above 15 eV.The resonance structures of state-selective charge-transfer cross sections arising from the competition among channels are analysed in detail.The radiative and nonradiative charge-transfer rate coefficients from low to high temperature are presented.     

Molecular dynamics study for the melting curve of MgO at high pressure

Shell-model molecular dynamics method is used to study the melting temperatures of MgO at elevated temperatures and high pressures using interaction potentials. Equations of state for MgO simulated by molecular dynamics are in good agreement with available experimental data. The pressure dependence of the melting curve of MgO has been calculated. The surface melting and superheating are considered in the correction of experimental data and the calculated values, respectively. The results of corrections are compared with those of previous work. The corrected melting temperature of MgO is consistent with corrected experimental measurements. The melting temperature of MgO up to 140GPa is calculated.     

A Microscopic Optical Potential for Deuteron

The microscopic optical potential for deuteron is obtained by folding the microscopic optical potentials of its constituent nucleons. The optical potential is used to predict the reaction cross sections and the elastic scattering angular distributions for some spherical target nuclei, and the results of theoretical calculation are compared with the experimental data available.     

Ep≤63 GeV 质子入射铅、铋引起的中子产生双微分截面的模拟(英文)

加速器驱动次临界系统(ADS) 液态Pb-Bi 散裂靶的设计中,需要可靠的理论计算工具精确地预言几个GeV 能量范围的质子引起的散裂反应产生的各种粒子和核素。利用蒙特卡罗模拟软件包Geant4 计算研究了800 MeV至3 GeV 质子入射铅、铋材料引起的中子产生双微分截面。比较了Geant4 不同物理模型得到的模拟结果与现有的实验数据。其中,Geant4 的QGSP BERT和QGSP INCL ABLA 物理模型模拟结果很好地再现了实验数据。本工作证实了Geant4 蒙特卡罗模拟软件包适合用于能量高达3 GeV 的质子入射铅、铋引起的中子产生双微分截面的模拟计算。A detailed design of the liquid Pb-Bi spallation target of the Accelerator Driven Systems (ADS) requires powerful and reliable computational tools that can accurately predict particles and nuclides production by the proton induced spallation reactions in the energy range of a few GeV. In this paper, the neutron production double-differential cross sections for Pb and Bi target materials at incident proton kinetic energies between 800 MeV and 3 GeV are studied by calculations with Monte Carlo simulation package Geant4. The simulated results of Geant4 with several physics models are compared with available experimental data. The simulated results generated by QGSP BERT and QGSP INCL ABLA physics models of Geant4 well reproduce the available experimental data. The present results validated that Geant4 Monte Carlo simulation package is suitable for simulations of neutron production double-differential cross sections of proton induced reaction on Pb and Bi targets in the incident energy range up to 3 GeV.     

New empirical formula for(γ, n) reaction cross section near GDR peak for elements with Z ≥ 60

A new empirical formula has been developed that describes the(7,n) nuclear reaction cross sections for isotopes with Z ≥ 60.The results were supported by calculations using TALYS-1.6 and EMPIRE-3.2.2 nuclear modular codes.The energy region for incident photon energy has been selected near the giant dipole resonance(GDR) peak energy.The evaluated empirical data were compared with available data in the experimental data library EXFOR.The data produced using TALYS-1.6 and EMPIRE-3.2.2 are in good agreement with experimental data.We have tested and presented the reproducibility of the present new empirical formula.We observe the reproducibility of the new empirical formula near the GDR peak energy is in good agreement with the experimental data and shows a remarkable dependency on key nuclei properties:the neutron,proton and atomic number of the nuclei.The behavior of nuclei near the GDR peak energy and the dependency of the GDR peak on the isotopic nature are predicted.An effort has been made to explain the deformation of the GDR peak in(γ,n) nuclear reaction cross sections for some isotopes,which could not be reproduced with TALYS-1.6 and EMPIRE-3.2.2.The evaluated data have been presented for the isotopes ~(180)W,~(183)W,~(202)Pb,~(203)Pb,~(204)Pb,~(205)Pb,~(231)Pa,~(232)U,~(237)U and ~(239)Pu,for which there are no previous measurements.     

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.     

Absolute Differential Cross Sections for Elastic Scattering of Electrons from CO at Intermediate and High Energies

The additivity rule model together with the complex optical model potential correlated by the concept of bonded atoms, which considers the overlapping effect of electron clouds between two atoms in a molecule, is firstly employed to calculate the absolute differential cross sections for electrons scattered by carbon monoxide at intermediate and high energies at the Hartree-Fock level. A comparison of elastic differential cross section results, obtained by using the correlated complex optical model potential, with the available experimental data,shows a significant improvement over the uncorrelated ones. The differential cross sections obtained by using thecorrelated complex optical model potential are in very good agreement with the experimental data. It is shown that the additivity rule model together with the correlated complex optical model potential is suitable for the calculations of the absolute differential cross sections of e-CO scattering.     

Dependence of Nucleon and Pion-Induced Fission Cross Sections on the Level Density Parameter in the Cascade-Exciton Model

A new method is used to compute the fission cross sections in which a change of the ratio of the level density parameter in fission to neutron emission channels is taken into account with the change of the incident energy of the projectile. It is shown that fission cross sections induced by nucleons and pions depend on the ratio of the level density parameter in the fission and evaporation modes, i,e. af /an, respectively. We are unable to describe well the cross sections for fission without using this new method. The computed values exhibit reasonable agreement with the experimental data found in the literature across a wide range of beam energies.     

Differential, elastic integral and moment transfer cross sections for electron scattering from N2 at intermediate- and high-energies

A complex optical model potential modified by incorporating the concept of bonded atom, with the overlapping effect of electron clouds between two atoms in a molecule taken into consideration, is firstly employed to calculate the differential cross sections, elastic integral cross sections, and moment transfer cross sections for electron scattering from molecular nitrogen over the energy range 300—1000eV by using additivity rule model at Hartree—Fock level. The bonded-atom concept is used in the study of the complex optical model potential composed of static, exchange, correlation polarization and absorption contributions. The calculated quantitative molecular differential cross sections, elastic integral cross sections, and moment transfer cross sections are compared with the experimental and theoretical ones wherever available, and they are found to be in good agreement with each other. It is shown that the additivity rule model together with the complex optical model potential modified by incorporating the concept of bonded atom is completely suitable for the calculations of differential cross section, elastic integral cross section and moment transfer cross section over the intermediate- and high-energy ranges.