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Coulomb exploded directional double ionization of N2O molecules in multicycle femtosecond laser pulses

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Chinese Physics B 2019年第9期28卷 22-26页

作者：马俊杨林康季琴颖张文斌李韩笑孙烽豪强俊杰陆培芬李辉宫晓春吴健 State Key Laboratory of Precision Spectroscopy East China Normal UniversityShanghai 200062China Collaborative Innovation Center of Extreme Optics Shanxi UniversityTaiyuan 030006China

We experimentally investigate Coulomb exploded directional double ionization of N2O molecules in elliptically polarized femtosecond laser pulses.The denitrogenation and deoxygenation channels are accessed via various pathways.It leads to distinct asymmetries in directional breaking of the doubly ionized N2O molecules versus the instantaneous laser field vector, which is revealed by tracing the sum-momentum spectra of the ionic fragments as a recoil of the ejected electrons.Our results demonstrate that the accessibility of the Coulomb exploded double ionization channels of N2O molecules are ruled by the detailed potential energy curves, and the directional emission of the fragments are governed by the joint effects of the electron localization-assisted enhanced ionization of the stretched molecules and the profiles of the molecular orbitals.

关键词： strong-field ionization directional molecular bond breaking ultrafast dynamics of molecules

Asymmetric structure of atomic above-threshold ionization spectrum in two-color elliptically polarized laser fields

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Chinese Physics B 2019年第10期28卷 183-191页

作者：周旭聪石尚李飞杨玉军陈京孟庆田王兵兵 School of Physics and Electronics Shandong Normal UniversityJinan 250358China Laboratory of Optical Physics Beijing National Laboratory for Condensed Matter PhysicsInstitute of PhysicsChinese Academy of SciencesBeijing 100190China Insititute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China HEDPS Center for Applied Physics and TechnologyPeking UniversityBeijing 100871China Institute of Applied Physics and Computational Mathematics Beijing 100088China University of Chinese Academy of Sciences Beijing 100049China

According to the frequency-domain theory, we investigate the asymmetric structure of above-threshold ionization(ATI) spectrum of an atom in two-color elliptically polarized(EP) laser fields. When both laser fields are linearly polarized(LP), the spectrum shows that the multi-plateau structure is symmetric about the emitted angle of electron at π/2, while the spectrum becomes asymmetric and shifts rightwards with the increase of the EP degree of the IR laser field. Since the total ATI process is regarded as including direct ATI and the rescattering ATI, we analyze the spectrum structure of direct ATI and rescattering ATI separately. Using the saddle-point approximation, we find that for direct ATI, the fringes on the spectrum are mainly attributed to the fact that the ionization probability becomes very small when the direction of emitted electrons is perpendicular to the direction of the XUV laser polarization;while for the rescattering ATI, the interference fringes on the spectrum mainly come from the superposition of the waist structures on the spectra of all sub-channels.

关键词： above-threshold ionization elliptically polarized two color laser fields asymmetric structure

Positron Impact ionization of Hydrogen, Sodium, and Potassium

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Chinese Physics Letters 1997年第5期14卷 348-351页

作者：周雅君潘守甫 Institute of Atomic and Molecular Physics National Laboratory of Theoretical and Computational ChemistryJilin UniversityChangchun 130023

The total ionization cross sections for positron scattering by hydrogen,sodium,and potassium are calculated by applying an equivalent-local optical potential model from the ionization threshold to 300eV.The total ionization cross sections are in excellent agreement with the recent measurements of Jones et al.The total ionization cross sections for sodium and potassium are compared with other theoretical calculations.

关键词： potassium ionization applying

Theoretical research on the transport and ionization rate coefficients in glow discharge dusty plasma

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Plasma Science and Technology 2020年第3期22卷 17-23页

作者：梁勇敢吴健李辉田瑞焕袁承勋王莹周忠祥田浩 School of Physics Harbin Institute of TechnologyHarbin 150001People’s Republic of China National Key Laboratory of Electromagnetic Environment(LEME) China Research Institute of Radio Wave PropagationBeijing 102206People’s Republic of China

The electron kinetic model for investigating the transport and ionization rate coefficients of argon glow discharge dusty plasma is developed from the Boltzmann equation.Both of the electron-neutral and electron-dust collisions are considered as collision terms in the kinetic equation.The kinetic equation is simplified by employing the local approximation and nonlocal approach under the same discharge conditions,and the corresponding simplified kinetic equations are known as local and nonlocal kinetic equations respectively.Then the electron energy distribution function(EEDF)is obtained by numerically solving the local and nonlocal kinetic equations and the dust charging equations simultaneously.Based on the obtained EEDFs,the effective electron temperature,electron mobility,electron diffusion coefficient and ionization rate coefficient are calculated for different discharge conditions.It is shown that the EEDFs calculated from the local kinetic model clearly differ from the nonlocal EEDFs and both the local and nonlocal EEDFs are also clearly different with Maxwellian distributions.The appearance of dust particles results in an obvious decrease of high energy electrons and increase of low energy electrons when axial electric field is low.With the increase of axial electric field,the influence of dust particles on the EEDFs becomes smaller.The electron mobility and diffusion coefficients calculated on the basis of local and nonlocal EEDFs do not differ greatly to the dust-free ones.While,when dust density nd=10^6 cm^?3,the electron mobility increases obviously compared with the dust-free results at low axial electric field and decreases with the increasing axial electric field until they are close to the dust-free ones.Meanwhile,electron diffusion coefficients for dusty case become smaller and decrease with the increasing axial electric field.The ionization rate coefficients decrease when dust particles are introduced and they approach the dust-free results gradually with the increasing axial electric field.

关键词： glow discharge dusty plasma kinetic model transport coefficient ionization rate coefficient

Measurement of K-Shell ionization Cross Sections of Cr, Ni and Cu Atoms by 7.5-25 keV Electron Impact

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Chinese Physics Letters 2001年第11期18卷 1460-1462页

作者：安竹唐昶环罗正明 Key Laboratory for Radiation Physics and Technology of Ministry of Education Institute of Nuclear Science and TechnologySichuan UniversityChengdu 610064

The K-shell ionization cross sections of Cr, Ni and Cu elements by 7.5-25 keV electron impact have been measured.The experimental data have also been compared with the theoretical predictions of the Hippler and Mayol-Salvat models. In general, it seems that the Mayol-Salvat model can provide a better description to our experimental data.

关键词： keV Electron ionization

Enhanced ionization of Linear Polyatomic Molecular Ions in Ultrashort Laser Fields

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Chinese Physics Letters 1999年第4期16卷 264-266页

作者：雷安乐倪国权黎忠翟华金徐至展 Shanghai Institute of Optics and Fine Mechanics Chinese Academy of SciencesShanghai 201800 Institute of Nuclear Physics and Chemistry P.O.Box 525-74Chengdu 610003

The ionization behavior of linear polyatomic molecular ions in ultrashort,intense laser fields was investigated with the time-dependent Schrodinger equation solved by the standard split-operator algorithm.The enhanced ionization effect was found as a general feature in the ions when the internuclear separation was in a critical distance range and can be explained in terms of the field-induced over-barrier ionization mechanism.In addition,the ionization energy does not influence the ionization probability significantly.

关键词： mechanism. ionization atomic

Recent Advances in Single-Cell Metabolomics Based on Mass Spectrometry

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CCS Chemistry 2023年第2期5卷 310-324页

作者： Qinlei Liu Sandra Martínez-Jarquín Renato Zenobi Department of Chemistry and Applied Biosciences ETH ZurichCH-8093 Zurich

Cellular heterogeneity is essential for the physiological functions of organisms,and precise interpretation of the relevant biological mechanisms involved requires accurate measurement of biomolecules,including DNA,RNA,proteins,and metabolites at the single-cell level.Cellular metabolites react most rapidly to environmental and biochemical changes such that their detection is a critical step in determining the physiological state of cells.However,their limited amounts,structural diversity,and significant content variation render single-cell metabolomics analysis technically challenging.Mass spectrometry,with its high sensitivity,good selectivity,and wide dynamic range,has been widely used in the single-cell analysis in recent years.In terms of ionization techniques,there are four main types of single-cell mass spectrometry methods:nano-electrospray ionization mass spectrometry,matrix-assisted laser desorption/ionization mass spectrometry,secondary ion mass spectrometry,and dielectric barrier discharge ionization mass spectrometry.In this mini review,the progress of single-cellmass spectrometrymethodologies and data processing strategies are summarized,and the future trends in single-cell mass spectrometry are outlined.

关键词： single-cell analysis metabolomics mass spectrometry ionization techniques analytical methods

Trajectory analysis of few-cycle strong field ionization in two-color circularly polarized fields

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Chinese Physics B 2019年第9期28卷 16-21页

作者：黄燕秦朝朝张逸竹王新成阎天民江玉海 College of Physics and Materials Science Henan Normal UniversityXinxiang 453007China Shanghai Advanced Research Institute Chinese Academy of SciencesShanghai 201210China University of Chinese Academy of Sciences Beijing 100049China ShanghaiTech University Shanghai 201210China Key Laboratory of Opto-electronics Information and Technical Science Tianjin UniversityTianjin 300072China

Bichromatic circularly polarized fields provide a useful tool to probe the ionization dynamics.In this work, we compare the photoelectron momentum distribution in few-cycle bichromatic field of different helicities.The spectral features are analyzed with semiclassical trajectories derived from the strong field approximation.In particular, the interference fringes in momentum distribution are investigated by tracking the ionization time and tunneling exits of released photoelectrons.Different types of trajectories that contribute to the interference fringes are elucidated.

关键词： strong field ionization semiclassical trajectories bicircularly polarized fields photoelectron momentum

Photoelectron imaging of resonance-enhanced multiphoton ionization and above-threshold ionization of ammonia molecules in a strong 800-nm laser pulse

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Chinese Physics B 2019年第6期28卷 140-145页

作者：宋乐乐孙亚楠王艳辉王晓春赫兰海罗嗣佐胡文惠佟秋男丁大军刘福春 Institute of Atomic and Molecular Physics Jilin UniversityChangchun 130012China Jilin Institute of Chemical Technology Changchun 132022China Jilin Provincial Key Laboratory of Applied Atomic and Molecular Spectroscopy Jilin UniversityChangchun 130012China College of Electronic Science and Engineering State Key Laboratory on Integrated OptoelectronicsJilin UniversityChangchun 130012China

In this work, we mainly investigate the NH3 molecular multiphoton ionization process by using the photoelectron velocity map imaging technique. Under the condition of femtosecond laser(wavelength at 800 nm), the photoelectron images are detected. The channel switching and above-threshold ionization(ATI) effect are also confirmed. The kinetic energy spectrum(KES) and the photoelectron angular distributions(PADs) are obtained through the anti-Abel transformation from the original images, and then three ionization channels are confirmed successfully according to the Freeman resonance effect in a relatively low laser intensity region. In the excitation process, the intermediate resonance Rydberg states are C^1 A 1(6 + 2 photons process), B^1 E(6 + 2 photons process) and C^1 A 1(7 + 2 photons process), respectively. At the same time, we also find that the photoelectron angular distributions are independent of laser intensity. In addition, the electrons produced by different processes interfere with each other and they can produce a spider-like structure. We also find ac-Stark movement according to the Stark-shift-induced resonance effect when the laser intensity is relatively high.

关键词： photoelectron imaging Rydberg state resonance-enhanced multiphoton ionization photoelectron angular distribution