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Precision calculation of low-energy electron-impact excitation cross sections of helium among the ground and excited states

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Physical Review A 2015年第2期91卷 022707-022707页

作者： De-Ling Zeng Xiang Gao Xiao-Ying Han Jia-Ming Li Key Laboratory for Laser Plasmas (Ministry of Education) and Department of Physics and Astronomy Shanghai Jiao Tong University Shanghai 200240 China Beijing Computational Science Research Center Beijing 100084 China Institute of Applied Physics and Computational Mathematics Beijing 100088 China Department of Physics and Center for Atomic and Molecular Nanosciences Tsinghua University Beijing 100084 China Collaborative Innovation Center of Quantum Matter Beijing 100084 China

Low-energy electron-impact cross sections of helium among the ground and some low excited states are calculated using the R-matrix method. The convergences of the cross sections are checked systematically by using five sets of high-quality target states; i.e., including 5, 11, 19, 29, and 39 physical target states, respectively. Our calculated cross sections are in excellent agreement with the benchmark high-resolution experimental data. Compared with the recommended theoretical data, there is a deviation of about 6%, which suggests the recommended data may need a revision. Based on our calculation results, the influence of the Rydberg target states on the collision cross sections of the excited states is found to be similar to the case of the ground state; i.e., the amplitude of resonance structures will decrease with respect to the principal quantum number n of Rydberg target states. This result should be very useful for providing the cross-section data in the whole energy regions with high quality, which would be of great importance in related scientific fields.

关键词： HELIUM ELECTRONIC excitation EXCITED states GROUND state (Quantum mechanics) CROSS sections (Nuclear physics) QUANTUM numbers

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Dynamical coupling of electrons and nuclei for Coulomb explosion of argon trimers in intense laser fields

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Physical Review A 2015年第2期92卷 023417-023417页

作者： Xiguo Xie Chengyin Wu Zongqiang Yuan Difa Ye Peng Wang Yongkai Deng Libin Fu Jie Liu Yunquan Liu Qihuang Gong Department of Physics and State Key Laboratory for Mesoscopic Physics Peking University Beijing 100871 People's Republic of China Collaborative Innovation Center of Quantum Matter Beijing 100871 People's Republic of China Institute of Applied Physics and Computational Mathematics 100088 Beijing People's Republic of China Center for Applied Physics and Technology Peking University 100084 Beijing People's Republic of China

We have experimentally and theoretically studied the fragmentation dynamics of argon trimer (Ar3) in intense laser fields. By coincidently measuring the momentum vectors, we obtained the emission geometry of the three fragmental ions produced in the three-body fragmentation process. In addition to the direct Coulomb explosion channels, we observed the indirect Coulomb explosion channels with Rydberg excitation. We have further developed a classical polyatomic molecular ensemble model, in which all interactions among electrons and nuclei are fully included, to simulate the fragmentation dynamics of argon trimer in intense laser fields. The experimental observations have been reproduced by the model calculation. The simulations show that the Rydberg excitation modifies the kinetic energy release as well as the emission geometry of fragmental ions during the explosion process. The study provides insight into the correlation dynamics of electrons and nuclei of many-body physics driven by intense laser fields.

关键词： COULOMB explosion ELECTRONS MOMENTUM distributions ARGON LASER beams NUCLEAR fragmentation

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Nonlinear saturation amplitude of cylindrical Rayleigh Taylor instability

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Chinese physics B 2014年第9期23卷 278-282页

作者：刘万海于长平叶文华王立峰 Research Center of Computational Physics Mianyang Normal University Key Laboratory of High Energy Density Physics Simulation (HEDPS) and Center for Applied Physics and TechnologyPeking University Key Laboratory of High Temperature Gas Dynamics (LHD) Institute of MechanicsChinese Academy of Sciences Institute of Applied Physics and Computational Mathematics Department of Physics Zhejiang University

The nonlinear saturation amplitude （NSA） of the fundamental mode in the classical Rayleigh-Taylor instability with a cylindrical geometry for an arbitrary Atwood number is analytically investigated by considering the nonlinear corrections up to the third order. The analytic results indicate that the effects of the initial radius of the interface （r0） and the Atwood number （A） play an important role in the NSA of the fundamental mode. The NSA of the fundamental mode first increases gently and then decreases quickly with increasing A. For a given A, the smaller the ro/λ（λ is the perturbation wavelength）, the larger the NSA of the fundamental mode. When ro/λ is large enough （r0 〉〉 λ）, the NSA of the fundamental mode is reduced to the prediction in the previous literatures within the framework of the third-order perturbation theory.

关键词： nonlinear saturation amplitude Rayleigh-Taylor instability cylindrical interface

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Generation of overdense and high-energy electron-positron-pair plasmas by irradiation of a thin foil with two ultraintense lasers

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Physical Review E 2015年第5期92卷 053107-053107页

作者： H. X. Chang B. Qiao Z. Xu X. R. Xu C. T. Zhou X. Q. Yan S. Z. Wu M. Borghesi M. Zepf X. T. He Center for Applied Physics and Technology HEDPS State Key Laboratory of Nuclear Physics and Technology and School of Physics Peking University Beijing 100871 China Collaborative Innovation Center of Extreme Optics Shanxi University Taiyuan Shanxi 030006 China Institute of Applied Physics and Computational Mathematics Beijing 100094 China Department of Physics and Astronomy Queen's University Belfast Belfast BT7 1NN United Kingdom

A scheme for enhanced quantum electrodynamics (QED) production of electron-positron-pair plasmas is proposed that uses two ultraintense lasers irradiating a thin solid foil from opposite sides. In the scheme, under a proper matching condition, in addition to the skin-depth emission of γ-ray photons and Breit-Wheeler creation of pairs on each side of the foil, a large number of high-energy electrons and photons from one side can propagate through it and interact with the laser on the other side, leading to much enhanced γ-ray emission and pair production. More importantly, the created pairs can be collected later and confined to the center by opposite laser radiation pressures when the foil becomes transparent, resulting in the formation of unprecedentedly overdense and high-energy pair plasmas. Two-dimensional QED particle-in-cell simulations show that electron-positron-pair plasmas with overcritical density 1022cm−3 and a high energy of 100s of MeV are obtained with 10 PW lasers at intensities 1023W/cm2, which are of key significance for laboratory astrophysics studies.

关键词： Irradiation Quantum electrodynamics Photons Electrons Energy density Astrophysics

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DiscreteMaximumPrinciple Based on Repair Technique for Finite Element Scheme of Anisotropic Diffusion Problems

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Advances in applied mathematics and Mechanics 2014年第6期6卷 849-866页

作者： Xingding Chen Guangwei Yuan Yunlong Yu Department of Mathematics School of ScienceBeijing Technology and Business UniversityBeijing 100048China LCP Institute of Applied Physics and Computational MathematicsP.O.Box 8009Beijing 100088China Institute of Applied Physics and Computational Mathematics P.O.Box 8009Beijing 100088China

In this paper,we construct a global repair technique for the finite element scheme of anisotropic diffusion equations to enforce the repaired solutions satisfying the discrete maximum *** is an extension of the existing local repair *** of the repair techniques preserve the total energy and are easy to be *** numerical experiments show that these repair techniques do not destroy the accuracy of the finite element scheme,and the computational cost of the global repair technique is cheaper than the local repair technique when the diffusion tensors are highly anisotropic.

关键词： Discrete maximum principle finite element scheme repair technique anisotropic diffusion problems

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Supernovae 2016bdu and 2005gl, and their link with SN 2009ip-like transients: another piece of the puzzle

arXiv

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arXiv 2017年

作者： Pastorello, A. Kochanek, C.S. Fraser, M. Dong, S. Elias-Rosa, N. Benetti, S. Cappellaro, E. Tomasella, L. Drake, A.J. Hermanen, J. Reynolds, T. Shappee, B.J. Smartt, S.J. Chambers, K.C. Huber, M.E. Smith, K. Stanek, K.Z. Filippenko, A.V. Christensen, E.J. Denneau, L. Djorgovski, S.G. Flewelling, H. Gall, C. Gal-Yam, A. Geier, S. Heinze, A. Holoien, T.W.-S. Isern, J. Kangas, T. Kankare, E. Koff, R.A. Llapasset, J.-M. Lowe, T.B. Lundqvist, P. Magnier, E.A. Mattila, S. Morales-Garoffolo, A. Mutel, R. Nicolas, J. Ochner, P. Ofek, E.O. Prosperi, E. Rest, A. Sano, Y. Stalder, B. Stritzinger, M.D. Taddia, F. Terreran, G. Tonry, J.L. Wainscoat, R.J. Waters, C. Weiland, H. Willman, M. Young, D.R. Zheng, W. INAF-Osservatorio Astronomico di Padova Vicolo dell’Osservatorio 5 PadovaI-35122 Italy Department of Astronomy Ohio State University 140 West 18th Avenue ColumbusOH43210 United States Ohio State University 191 W. Woodruff Ave. ColumbusOH43210 United States School of Physics O’Brien Centre for Science North University College Dublin Belfield Dublin 4 Ireland Institute of Astronomy University of Cambridge Madingley Road CambridgeCB3 0HA United Kingdom Royal Society – Science Foundation Ireland University Research Fellow Kavli Institute for Astronomy and Astrophysics Peking University Yi He Yuan Road 5 Hai Dian District Beijing100871 China Astronomy Department California Institute of Technology PasadenaCA91125 United States Tuorla Observatory Department of Physics and Astronomy University of Turku Väisäläntie 20 PiikkiöFI-21500 Finland Nordic Optical Telescope Apartado 474 Santa Cruz de La PalmaE-38700 Spain Carnegie Observatories 813 Santa Barbara Street PasadenaCA91101 United States Hubble Fellow and Carnegie-Princeton Fellow Astrophysics Research Centre School of Mathematics and Physics Queen’s University Belfast BelfastBT7 1NN United Kingdom Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States Department of Astronomy University of California BerkeleyCA94720-3411 United States Lunar and Planetary Lab Department of Planetary Sciences University of Arizona TucsonAZ85721 United States Dark Cosmology Centre Niels Bohr Institute University of Copenhagen Juliane Maries Vej 30 Copenhagen2100 Denmark Department of Physics and Astronomy Aarhus University Ny Munkegade 120 Aarhus CDK-8000 Denmark Department of Particle Physics and Astrophysics Faculty of Physics Weizmann Institute of Science Rehovot76100 Israel Cuesta de San José s/n Breña Baja La PalmaE-38712 Spain Instituto de Astrofísica de Canarias Vía Láctea s/n La Laguna TenerifeE-38200 Spain US Department of Energy Computatio

Supernova (SN) 2016bdu is an unusual transient resembling SN 2009ip. SN 2009ip-like events are characterized by a long-lasting phase of erratic variability which ends with two luminous outbursts a few weeks apart. The second outburst is significantly more luminous (about 3 mag) than the first. In the case of SN 2016bdu, the first outburst (Event A) reached an absolute magnitude Mr ≈ −15.3 mag, while the second one (Event B) occurred over one month later and reached Mr ≈ −18 mag. By inspecting archival data, a faint source at the position of SN 2016bdu is detectable several times in the past few years. We interpret these detections as signatures of a phase of erratic variability, similar to that experienced by SN 2009ip between 2008 and mid-2012, and resembling the currently observed variability of the luminous blue variable SN 2000ch in NGC 3432. Spectroscopic monitoring of SN 2016bdu during the second peak initially shows features typical of a SN IIn. One month after the Event B maximum, the spectra develop broad Balmer lines with P Cygni profiles and broad metal features. At these late phases, the spectra resemble those of a typical Type II SN. All members of this SN 2009ip-like group are remarkably similar to the Type IIn SN 2005gl. For this object, the claim of a terminal SN explosion is supported by the disappearance of the progenitor star. The similarity with SN 2005gl suggests that all members of this family may finally explode as genuine SNe, although the unequivocal detection of nucleosynthesised elements in their nebular spectra is still missing. Copyright © 2017, The Authors. All rights reserved.

关键词： Supernovae

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Cloudless atmospheres for young low-gravity substellar objects

arXiv

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arXiv 2017年

作者： Tremblin, P. Chabrier, G. Baraffe, I. Liu, Michael C. Magnier, E.A. Lagage, P.-O. De Oliveira, C. Alves Burgasser, A.J. Amundsen, D.S. Drummond, B. Maison de la Simulation CEA CNRS Univ. Paris-Sud UVSQ Université Paris-Saclay Gif-sur-Yvette91191 France Astrophysics Group University of Exeter ExeterEX4 4QL United Kingdom Ecole Normale Supérieure de Lyon CRAL UMR CNRS 5574 Lyon Cedex 0769364 France Institute for Astronomy University of Hawaii 2680 Woodlawn Drive HonoluluHI96822 United States Infrared Telescope Facility University of Hawaii National Aeronautics and Space Administration Science Mission Directorate Planetary Astronomy Program Irfu CEA Université Paris-Saclay Gif-sur YvetteF-9119 France Université Paris Diderot AIM Sorbonne Paris Cité CEA CNRS Gif-sur-YvetteF-91191 France European Space Agency c/o STScI 3700 San Martin Drive BaltimoreMD21218 United States UC San Diego M/C 0424 9500 Gilman Drive La JollaCA92093 United States Department of Applied Physics and Applied Mathematics Columbia University New YorkNY10025 United States NASA Goddard Institute for Space Studies New YorkNY10025 United States

Atmospheric modeling of low-gravity (VL-G) young brown dwarfs remains a challenge. The presence of very thick clouds has been suggested because of their extremely red near-infrared (NIR) spectra, but no cloud models provide a good fit to the data with a radius compatible with evolutionary models for these objects. We show that cloudless atmospheres assuming a temperature gradient reduction caused by fingering convection provides a very good model to match the observed VL-G NIR spectra. The sequence of extremely red colors in the NIR for atmospheres with e_ective temperature from ∼ 2000 K down to ∼ 1200 K is very well reproduced with predicted radii typical of young low-gravity objects. Future observations with NIRSPEC and MIRI on the James Webb Space Telescope (JWST) will provide more constrains in the mid-infrared, helping to confirm/refute whether or not the NIR reddening is caused by fingering convection. We suggest that the presence/absence of clouds will be directly determined by the silicate absorption features that can be observed with MIRI. JWST will therefore be able to better characterize the atmosphere of these hot young brown dwarfs and their low-gravity exoplanet analogues. Copyright © 2017, The Authors. All rights reserved.

关键词： Infrared devices

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A Simple Framework of Conservative Algorithms for the Coupled Nonlinear Schrdinger Equations with Multiply Components

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Communications in Theoretical physics 2014年第6期61卷 703-709页

作者：钱旭宋松和李伟斌 Department of Mathematics and Systems Science National University of Defense Technology Program in Applied and Computational Mathematics Princeton University State Key Laboratory of High Performance Computing National University of Defense Technology

Considering the coupled nonlinear Schr¨odinger system with multiply components, we provide a novel framework for constructing energy-preserving algorithms. In detail, based on the high order compact finite difference method, Fourier pseudospectral method and wavelet collocation method for spatial discretizations, a series of high accurate conservative algorithms are presented. The proposed algorithms can preserve the corresponding discrete charge and energy conservation laws exactly, which would guarantee their numerical stabilities during long time ***, several analogous multi-symplectic algorithms are constructed as comparison. Numerical experiments for the unstable plane waves will show the advantages of the proposed algorithms over long time and verify the theoretical analysis.

关键词： conservative algorithm coupled nonlinear SchrSdinger equation multiply components unstablewave

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Single-point kinetic energy density functionals: A pointwise kinetic energy density analysis and numerical convergence investigation

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Physical Review B 2015年第4期91卷 045124-045124页

作者： Junchao Xia Emily A. Carter Department of Mechanical and Aerospace Engineering Princeton University Princeton New Jersey 08544-5263 USA Program in Applied and Computational Mathematics and Andlinger Center for Energy and the Environment Princeton University Princeton New Jersey 08544-5263 USA

We present a comprehensive study of single-point kinetic energy density functionals (KEDFs) to be used in orbital-free density functional theory (DFT) calculations. We first propose a form of KEDFs based on a pointwise Kohn-Sham (KS) kinetic energy density (KED) and electron localization function (ELF) analysis. We find that the ELF and modified enhancement factor have a very strong and transferable correlation with the reduced density in various bulk metals. The non-self-consistent kinetic energy errors predicted by our KEDF models are decreased greatly compared to previously reported generalized gradient approximation (GGA) KEDFs. Second, we perform self-consistent calculations with various single-point KEDFs and investigate their numerical convergence behavior. We find striking numerical instabilities for previous GGA KEDFs; most of the GGA KEDFs fail to converge and show unphysical densities during the optimization. In contrast, our KEDFs demonstrate stable convergence, and their self-consistent results of various bulk properties agree reasonably well with KSDFT. A further detailed KED analysis reveals an interesting bifurcation phenomenon in defective metals and alloys, which may shed light on directions for future KEDF development.

关键词： KINETIC energy DENSITY functionals DENSITY functional theory ELECTRON research BIFURCATION theory

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Reply to “Comment on ‘Single-point kinetic energy density functionals: A pointwise kinetic energy density analysis and numerical convergence investigation’ ”

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Physical Review B 2015年第11期92卷 117102-117102页

We find that the multivalued character of the G factor as a function of the reduced gradient (s) still exists after accounting for pseudopotential artifacts and the kinetic energy global upper bound. We also find that the VT84F functional indeed exhibits stable convergence and more reasonable results for self-consistent bulk properties compared to other generalized gradient approximation (GGA) kinetic energy density functionals (KEDFs) that we tested earlier. However, VT84F generally yields overestimated equilibrium volumes, which may result from its inability (as with all GGAs) to reproduce the G−s multivalued character. The analogous failure to predict the multivalued character of G as a function of the reduced density (d) is also likely to be responsible for the inaccuracy of our vWGTF functionals reported earlier. Our multivaluedness analysis therefore does not impugn any particular GGA KEDF. Instead, it merely confirms the importance of pointwise analysis for improving KEDFs by emphasizing the need to resolve the multivaluedness of G with respect to various density variables.

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