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Spectroscopy and scattering matrices with nitrogen atom:Rydberg states and optical oscillator strengths

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Chinese Physics B 2022年第4期31卷 261-266页

作者： Yuhao Zhu Rui Jin Yong Wu Jianguo Wang Key Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsBeijing 100088China Center for Free-Electron Laser Science DESYHamburg 22607Germany HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100084China

The scattering matrices of e+N^(+)with J^(π)=1.5^(+)in discrete energy regions are calculated using the eigenchannel R-matrix *** obtain good parameters of multichannel quantum defect theory(MQDT)that vary smoothly as the function of the energy resulting from the analytical continuation property of the scattering *** employing the MQDT,all discrete energy levels for N could be calculated accurately without missing *** MQDT parameters(i.e.,scattering matrices)can be calibrated with the available precise spectroscopy *** this work,the optical oscillator strengths for the transition between the ground state and Rydberg series are obtained,which provide rich data for the diagnostic analysis of plasma.

关键词： eigenchannel R-matrix oscillator strengths

Structural,electronic,and magnetic properties of vanadium atom-adsorbed MoSe2 monolayer

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Chinese Physics B 2017年第2期26卷 392-398页

作者： Ping Llu Zhen-Zhen Qin Yun-Liang Yue Xu Zuo College of Electronic Information and Optical Engineering Nankai University Tianjin 300071 China

Using the first-principles calculations, we study the structural, electronic, and magnetic properties of vanadium adsorbed MoSe_2 monolayer, and the magnetic couplings between the V adatoms at different adsorption concentrations. The calculations show that the V atom is chemically adsorbed on the MoSe_2 monolayer and prefers the location on the top of an Mo atom surrounded by three nearest-neighbor Se atoms. The interatomic electron transfer from the V to the nearestneighbor Se results in the polarized covalent bond with weak covalency, associated with the hybridizations of V with Se and Mo. The V adatom induces local impurity states in the middle of the band gap of pristine MoSe_2, and the peak of density of states right below the Fermi energy is associated with the V- dz^2 orbital. A single V adatom induces a magnetic moment of 5 μBthat mainly distributes on the V-3d and Mo-4d orbitals. The V adatom is in high-spin state, and its local magnetic moment is associated with the mid-gap impurity states that are mainly from the V-3d orbitals. In addition,the crystal field squashes a part of the V-4s electrons into the V-3d orbitals, which enhances the local magnetic *** magnetic ground states at different adsorption concentrations are calculated by generalized gradient approximations（GGA） and GGA＋U with enhanced electron localization. In addition, the exchange integrals between the nearest-neighbor V adatoms at different adsorption concentrations are calculated by fitting the first-principle total energies of ferromagnetic（FM） and antiferromagnetic（AFM） states to the Heisenberg model. The calculations with GGA show that there is a transition from ferromagnetic to antiferromagnetic ground state with increasing the distance between the V adatoms. We propose an exchange mechanism based on the on-site exchange on Mo and the hybridization between Mo and V, to explain the strong ferromagnetic coupling at a short distance between the V adatoms. However, the ferromagneti

关键词： V-adatom MoSe2 monolayer magnetic moment magnetic coupling first-principles calculation

A general framework for describing photofission observables of actinides at an average excitation energy below 30 MeV

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Chinese Physics C 2022年第8期46卷 170-183页

作者： Guan-Lin Wang Hao-Yang Lan Xiao-Ming Shi Zhi-Chao Zhu Wen Luo School of Nuclear Science and Technology University of South ChinaHengyang 421001China

A reasonable prediction of photofission observables plays a paramount role in understanding the photofission process and guiding various photofission-induced applications,such as short-lived isotope production,nuclear waste disposal,and nuclear ***,the available experimental data for photofission observables are limited,and the existing models and programs have mainly been developed for neutron-induced fission *** this study,a general framework is proposed for characterizing the photofission observables of actinides,including the mass yield distributions(MYD) and isobaric charge distributions(ICD) of fission fragments and the multiplicity and energy distributions of prompt neutrons(n_(p)) and prompt γ rays(γ_(p)).The framework encompasses various systematic neutron models and empirical models considering the Bohr hypothesis and does not rely on the experimental data as *** models are then validated individually against experimental data at an average excitation energy below 30 MeV,which shows the reliability and robustness of the general ***,we employ this framework to predict the characteristics of photofission fragments and the emissions of prompt particles for typical actinides including ^(232)Th,^(235,238)U and ^(240)*** is found that the ^(238)U(γ,f) reaction is more suitable for producing neutron-rich nuclei compared to the ^(232)Th(γ,f) *** addition,the average multiplicity number of both n_(p) and yp increases with the average excitation energy.

关键词： general framework photofission observables mass yield distributions isobaric charge distributions prompt neutron andγrays

Design and optimization of a SiC thermal emitter/absorber composed of periodic microstructures based on a non-linear method

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Chinese Physics B 2015年第9期24卷 276-283页

作者：王卫杰赵振国赵艺周海京符策基 Institute of Applied Physics and Computational Mathematics Software Center for High Performance Numerical Simulation of caep Complicated Electromagnetic Environment Laboratory of caep LTCS and Department of Mechanics and Engineering Science College of EngineeringPeking University

Spectral and directional control of thermal emission based on excitation of confined electromagnetic resonant modes paves a viable way for the design and construction of microscale thermal emitters/absorbers. In this paper, we present numerical simulation results of the thermal radiative properties of a silicon carbide（Si C） thermal emitter/absorber composed of periodic microstructures. We illustrate different electromagnetic resonant modes which can be excited with the structure,such as surface phonon polaritons, magnetic polaritons and photonic crystal modes, and the process of radiation spectrum optimization based on a non-linear optimization algorithm. We show that the spectral and directional control of thermal emission/absorption can be efficiently achieved by adjusting the geometrical parameters of the structure. Moreover, the optimized spectrum is insensitive to 3% dimension modification.

关键词： silicon carbide radiative heat transfer photonic crystal optimization method

Energy loss of tens keV charged particles traveling in the hot dense carbon plasma

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Science China(Physics,Mechanics & Astronomy) 2016年第8期59卷 65-72页

作者： ZhenGuo Fu ZhiGang Wang Bin He DaFang Li Ping Zhang Center for Fusion Energy Science and Technology Chinese Academy of Engineering Physics Beijing 100088 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China

The energy loss of charged particles, including electrons, protons, and α-particles with tens keV initial energy E0, traveling in the hot dense carbon(C) plasma for densities from 2.281 to 22.81 g/cm3 and temperatures from 400 to 1500 eV is systematically and quantitatively studied by using the dimensional continuation method. The behaviors of different charged particles are readily distinguishable from each other. Firstly, because an ion is thousands times heavier than an electron, the penetration distance of the electron is much longer than that of proton and α-particle traveling in the plasma. Secondly, most energy of electron projectile with E0 projectile particle can be clearly found from the fitted *** believe that with the advanced progress of the present experimental technology, the findings shown here could be confirmed in ion-stopping experiments in the near future.

关键词： stopping power BPS model inertial confinement fusion dense plasmas

Picard-Newton Iterative Method with Time Step Control for Multimaterial Non-Equilibrium Radiation Diffusion Problem

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Communications in Computational Physics 2011年第9期10卷 844-866页

作者： Jingyan Yue Guangwei Yuan National Key Laboratory of Science and Technology on Computational Physics Institute of Applied Physics and Computational MathematicsP.O.Box 8009Beijing 100088China

For a new nonlinear iterative method named as Picard-Newton(P-N)iterative method for the solution of the time-dependent reaction-diffusion systems,which arise in non-equilibrium radiation diffusion applications,two time step control methods are investigated and a study of temporal accuracy of a first order time integration is *** non-equilibrium radiation diffusion problems with flux limiter are considered,which appends pesky complexity and nonlinearity to the diffusion *** results are presented to demonstrate that compared with Picard method,for a desired accuracy,significant increase in solution efficiency can be obtained by Picard-Newton method with the suitable time step size selection.

关键词： Non-equilibrium radiation diffusion Picard Picard-Newton based on linearizationdiscretization nonlinear iterative method time step control

research ANNOUNCEMENTS High Order Numerical Solution of Integral Transport Equation in Slab Geometry

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数学进展 2002年第3期31卷 287-289页

作者：沈智军袁光伟沈隆钧 Laboratory of Computational Physics Institute of Applied Physics and Computational MathematicsP.O.Box.8009Beijing100088P.R.China

There are some common numerical methods for solving neutron transport equation,whichillCllldillg th6 W6ll-kll。Wll diSCf6t6 Ofdlll&bS th6thod,PN sppTOXlth3t1Oll slid flit6grsl if3llspOYtmethods[1].There exists certain singularities In the solution oftransport e叩ation near theboundary and interfacep].It gives rise to the difficulty In the construction ofhlgh order accuratenumerical *** numerical solution obtained by n。

关键词：积分迁移方程 Slab几何数值解中子迁移方程

First-principles calculations of F-, Cl-, and N-related defects of amorphous SiO_(2) and their impacts on carrier trapping and proton release

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Chinese Physics B 2021年第4期30卷 453-458页

作者： Xin Gao Yunliang Yue Yang Liu Xu Zuo College of Electronic Information and Optical Engineering Nankai UniversityTianjin 300071China School of Information Engineering Yangzhou UniversityYangzhou 225127China Microsystem and Terahertz research Center China Academy of Engineering PhysicsChengdu 610200China Institute of Electronic Engineering China Academy of Engineering PhysicsMianyang 621999China Municipal Key Laboratory of Photo-electronic Thin Film Devices and Technology Nankai UniversityTianjin 300071China Engineering research Center of Thin Film Optoelectronics Technology Ministry of EducationTianjin 300071China

The first-principles calculations based on density functional theory are performed to study F-,Cl-,and N-related defects of amorphous SiO_(2)(a-SiO_(2)) and their impacts on carrier trapping and proton *** possible geometric configurations of the impurity-related defects,the formation energies,the hole or electron trapping of the neutral defects,and the mechanisms to suppress proton diffusion by doping N are *** is demonstrated by the calculations that the impurity atoms can interact with the oxygen vacancies and result in impurity-related *** reactions can be utilized to saturate oxygen vacancies that will cause ionization damage to the semiconducting ***,the calculated formation energy indicates that the F-or Cl-related oxygen vacancy defect is a deep hole trap,which can trap holes and prevent them from diffusing to the a-SiO_(2)/Si ***,three N-related defects,namely N(2)o-H,N(2)o=O,and N(3)o-Vo,tend to act as shallow hole traps to facilitate hole transportation during device *** N(2)o and N(3)o configurations can be negatively charged as deep electron traps during the oxide charge buildup after ionization *** addition,the nudged elastic band(NEB) calculations show that four N-related defects,namely N(2)o,N(2)o-H,N(2)o=O,and N(3)o are capable of capturing protons and preventing them from diffusing to and de-passivating the *** research reveals the fundamental properties of the F-,Cl-,and N-related defects in amorphous silica and the details of the reactions of the carrier trapping and proton *** findings help to understand the microscopic mechanisms that alleviate ionization damage of semiconducting devices by doping a-SiO_(2).

关键词： first-principles calculation doping defect proton

Rapid interrogation of special nuclear materials by combining scattering and transmission nuclear resonance fluorescence spectroscopy

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Nuclear Science and Techniques 2021年第8期32卷 67-77页

作者： Hao-Yang Lan Tan Song Jia-Lin Zhang Jian-Liang Zhou Wen Luo School of Nuclear Science and Technology University of South ChinaHengyang 421001China National Exemplary Base for International Sci.&Tech. Collaboration of Nuclear Energy and Nuclear SafetyUniversity of South ChinaHengyang 421001China

The smuggling of special nuclear materials(SNMs)across national borders is becoming a serious threat to nuclear *** paper presents a feasibility study on the rapid interrogation of concealed SNMs by combining scattering and transmission nuclear resonance fluorescence(s NRF and t NRF)*** s NRF spectroscopy,SNMs such as^(235,238)U are excited by a wide-band photon beam of appropriate energy and exhibit unique NRF *** Carlo simulations show that one-dimensional scans can realize isotopic identification of concealed^(235,238)U when the detector array used for interrogation has sufficiently high energy *** simulated isotopic ratio^(235U/238)U is in good agreement with the theoretical value when the SNMs are enclosed in relatively thin *** interrogation is followed by t NRF spectroscopy using a narrow-band photon beam with the goal of obtaining tomographic images of the concealed *** reconstructed image clearly reveals the position of the isotope^(235)U inside an iron *** is shown that the interrogation time of s NRF and t NRF spectroscopy is one order of magnitude lower than that when only t NRF spectroscopy is used and results in a missed-detection rate of 10^(-3).The proposed method can also be applied for isotopic imaging of other SNMs such as^(239,240)Pu and^(237)Np.

关键词： Special nuclear material Nondestructive interrogation Nuclear resonance fluorescence