The ionization potential (IP) is a basic property of an atom, which has many applications such as in element analysis. With the Dirac-Slater methods (i.e., mean field theory), IPs of all occupied orbitals for elem...The ionization potential (IP) is a basic property of an atom, which has many applications such as in element analysis. With the Dirac-Slater methods (i.e., mean field theory), IPs of all occupied orbitals for elements with atomic number (Z ≤ 119) are calculated conveniently and systematically. Compared with available experimental measurements, the theoretical accuracies of IPs for various occupied orbitals are ascertained. The map of the inner orbital IPs with Mood accuracies should be useful to select x-ray energies for element analysis. Based on systematic variations of the first IPs for the outermost orbitals in good agreement with experimental values as well as other IPs, mechanisms of electronic configurations of all atomic elements (Z ≤ 119) along the periodic table are elucidated. It is interesting to note that there exist some deficiencies of the intermediate orbital IPs, which are due to electron correlations and should be treated beyond the mean field theory.展开更多
A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system an...A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part(ne ≥ 8–9 × 10^19cm^-3) of the flow is directly measured to be of ~ 10^6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part(ne ≤ 2 × 10^19cm^-3) can be estimated as ~ 10^7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.展开更多
The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ...The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ensemble of electrons in such screened Coulomb potentials and circularly polarized laser fields. Simulations show that electron trajectories are bent by Coulomb fields, resulting in the laser-intensity-dependent drift of photoelectron momentum distributions in the laser polarization plane. This study intuitively explains how Coulomb potentials modify photoelectron momenta.展开更多
A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e....A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.展开更多
The first experimental measurements of intense(~7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The tot...The first experimental measurements of intense(~7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The total energy of the THz radiation is found to decrease by approximately a factor of 2 compared to a cold target reference. This is attributed to an increase in the scale length of the preformed plasma, driven by proton heating, at the front surface of the target,where the THz radiation is generated. The results show the importance of controlling the preplasma scale length for THz production.展开更多
High-order harmonic generation (HOHG) from the inter- actions of relativistically intense laser pulses with solid-density plasma surfaces has been demonstrated as a promising bright coherent x-ray source in the last...High-order harmonic generation (HOHG) from the inter- actions of relativistically intense laser pulses with solid-density plasma surfaces has been demonstrated as a promising bright coherent x-ray source in the last de- cade. In contrast with the harmonic generation from la- ser-gas interactions,展开更多
A slim optical fingerprint recognition sensor(OFRS) based on a grating input coupler and a microprism sensing surface is proposed.By using a subwavelength grating coupler,input light is coupled into the planar waveg...A slim optical fingerprint recognition sensor(OFRS) based on a grating input coupler and a microprism sensing surface is proposed.By using a subwavelength grating coupler,input light is coupled into the planar waveguide and the propagation angle is well engineered to avoid image overlap,thus an undistorted fingerprint is captured.For maintaining a thin structure,a microprism array is utilized to facilitate the breaking of total internal reflection under a large diffraction angle from the grating.The feasibility,efficiency,and image quality of the proposed structure are verified and discussed.The device has the advantages of a slim structure,a high image contrast,and a compact architecture,suitable for mobile devices.展开更多
Due to the existence of spatial walk-off and/or group-velocity mismatch effects, pump-to-signal phase transfer becomes inevitable during parametric amplification. We experimentally demonstrate that in hybrid seeded op...Due to the existence of spatial walk-off and/or group-velocity mismatch effects, pump-to-signal phase transfer becomes inevitable during parametric amplification. We experimentally demonstrate that in hybrid seeded optical parametric amplifiers(OPAs) that include two OPA stages seeded by the signal and idler waves, respectively, the phase of the output signal can be restored to its initial value, although there are spatial and temporal phase fluctuations on the pump source. This method significantly relaxes the requirement for high pump beam quality, which is always very stringent in parametric amplification systems. With the introduction of this scheme into birefringent phase-matching OPAs or chirped-pulse OPAs, it should be promising to achieve intense femtosecond laser pulses that are close to the diffraction limit in space and ultra-high contrast in time, simultaneously.展开更多
Ultrashort multi-ke V x-ray pulses are generated by electron plasma produced by the irradiation of femtosecond pulses on metals. These sub-picosecond x-ray pulses have extended the field of x-ray spectroscopy into the...Ultrashort multi-ke V x-ray pulses are generated by electron plasma produced by the irradiation of femtosecond pulses on metals. These sub-picosecond x-ray pulses have extended the field of x-ray spectroscopy into the femtosecond time domain. However, pulse-to-pulse instability and long data acquisition time restrict the application of ultrashort x-ray systems operating at low repetition rates. Here we report on the performance of a femtosecond laser plasma-induced hard x-ray source that operates at 1-k Hz repetition rate, and provides a flux of 2.0 × 10^10 photons/s of Cu Kαradiation. Using this system for time-resolved x-ray diffraction experiments, we record in real time, the transient processes and structural changes induced by the interaction of 400-nm femtosecond pulse with the surface of a 200-nm thick Au(111) single crystal.展开更多
基金Supported by the Ministry of Science and Technology and Ministry of Education of Chinathe Key Grant Project of Chinese Ministry of Education under Grant No 306020+2 种基金the National Natural Science Foundation of China under Grant Nos 11274035 and 11328401the National High-Tech ICF Committee in China,the Yin-He Super-computer Center,Institute of Applied Physics and Mathematicsthe National Basic Research Program of China under Grant No 2011CB921501
文摘The ionization potential (IP) is a basic property of an atom, which has many applications such as in element analysis. With the Dirac-Slater methods (i.e., mean field theory), IPs of all occupied orbitals for elements with atomic number (Z ≤ 119) are calculated conveniently and systematically. Compared with available experimental measurements, the theoretical accuracies of IPs for various occupied orbitals are ascertained. The map of the inner orbital IPs with Mood accuracies should be useful to select x-ray energies for element analysis. Based on systematic variations of the first IPs for the outermost orbitals in good agreement with experimental values as well as other IPs, mechanisms of electronic configurations of all atomic elements (Z ≤ 119) along the periodic table are elucidated. It is interesting to note that there exist some deficiencies of the intermediate orbital IPs, which are due to electron correlations and should be treated beyond the mean field theory.
基金Project supported by the National Basic Research Program of China(Grant No.2013 CBA01501/3)the National Natural Science Foundation of China(Grant Nos.11503041,11135012,11375262,11573040,11574390,and 11220101002)China Postdoctoral Science Foundation(Grant No.2015M571124)
文摘A counter-streaming flow system is a test-bed to investigate the astrophysical collisionless shock(CS) formation in the laboratory. Electrostatic/electromagnetic instabilities, competitively growing in the system and exciting the CS formation, are sensitive to the flows parameters. One of the most important parameters is the velocity, determining what kind of instability contributes to the shock formation. Here we successfully measure the evolution of the counter-streaming flows within one shot using a multi-pulses imaging diagnostic technique. With the technique, the average velocity of the high-density-part(ne ≥ 8–9 × 10^19cm^-3) of the flow is directly measured to be of ~ 10^6cm/s between 7 ns and 17 ns.Meanwhile, the average velocity of the low-density-part(ne ≤ 2 × 10^19cm^-3) can be estimated as ~ 10^7cm/s. The experimental results show that a collisionless shock is formed during the low-density-part of the flow interacting with each other.
基金supported by the National Natural Science Foundation of China(Grant Nos.11104180,11175120,11121504,and 11322438)the Fok Ying-Tong Education Foundation for Young Teachers in the Higher Education Institutions of China(Grant No.131010)
文摘The photoelectron momentum distribution of H+ in circularly polarized laser fields is studied based on classical trajectory calculations. We screen Coulomb potentials at different radii, and trace trajectories of an ensemble of electrons in such screened Coulomb potentials and circularly polarized laser fields. Simulations show that electron trajectories are bent by Coulomb fields, resulting in the laser-intensity-dependent drift of photoelectron momentum distributions in the laser polarization plane. This study intuitively explains how Coulomb potentials modify photoelectron momenta.
基金supported by the National Basic Research Program of China(Grant Nos.2011CB921501 and 2013CB922200)the National Natural Science Foundation of China(Grant Nos.11274035,11275029,11328401,11371218,11474031,11474032,and 11474034)the Foundation of Development of Science and Technology of Chinese Academy of Engineering Physics(Grant Nos.2013A0102005 and 2014A0102005)
文摘A method to deal with the electron impact excitation cross sections of an atom from low to high incident energies are presented. This method combines the partial wave method and the first Born approximation(FBA), i.e., replacing the several lowest partial wave cross sections of the total cross sections within FBA by the corresponding exact partial wave cross sections. A new set of codes are developed to calculate the FBA partial wave cross sections. Using this method,the convergent e–He collision cross sections of optical-forbidden and optical-allowed transitions at low to high incident energies are obtained. The calculation results demonstrate the validity and efficiency of the method.
基金supported by National Basic Research Program of China (grant nos. 2013CBA01500 and 2014CB339801)National Natural Science Foundation of China (grant nos. 11121504, 11205100, 11220101002 and 11135012)+1 种基金the EPSRC (grant nos. EP/J003832/1 and EP/L001357/1)the Swedish Research Council
文摘The first experimental measurements of intense(~7 × 1019 W cm-2) laser-driven terahertz(THz) radiation from a solid target which is preheated by an intense pulse of laser-accelerated protons is reported. The total energy of the THz radiation is found to decrease by approximately a factor of 2 compared to a cold target reference. This is attributed to an increase in the scale length of the preformed plasma, driven by proton heating, at the front surface of the target,where the THz radiation is generated. The results show the importance of controlling the preplasma scale length for THz production.
基金supported by the National Basic Research Program of China(No.2013CBA01502)the National Natural Science Foundation of China(Nos.11305103,11374209,11374210,and 11205100)+1 种基金the Natural Science Foundation of Shanghai(No.13ZR1456300)the International Science&Technology Cooperation Program of China(No.2014DFG02330)
文摘High-order harmonic generation (HOHG) from the inter- actions of relativistically intense laser pulses with solid-density plasma surfaces has been demonstrated as a promising bright coherent x-ray source in the last de- cade. In contrast with the harmonic generation from la- ser-gas interactions,
基金supported by the National Natural Science Foundation of China under Nos.61370047,11374212,51235007,and 11421064
文摘A slim optical fingerprint recognition sensor(OFRS) based on a grating input coupler and a microprism sensing surface is proposed.By using a subwavelength grating coupler,input light is coupled into the planar waveguide and the propagation angle is well engineered to avoid image overlap,thus an undistorted fingerprint is captured.For maintaining a thin structure,a microprism array is utilized to facilitate the breaking of total internal reflection under a large diffraction angle from the grating.The feasibility,efficiency,and image quality of the proposed structure are verified and discussed.The device has the advantages of a slim structure,a high image contrast,and a compact architecture,suitable for mobile devices.
文摘Due to the existence of spatial walk-off and/or group-velocity mismatch effects, pump-to-signal phase transfer becomes inevitable during parametric amplification. We experimentally demonstrate that in hybrid seeded optical parametric amplifiers(OPAs) that include two OPA stages seeded by the signal and idler waves, respectively, the phase of the output signal can be restored to its initial value, although there are spatial and temporal phase fluctuations on the pump source. This method significantly relaxes the requirement for high pump beam quality, which is always very stringent in parametric amplification systems. With the introduction of this scheme into birefringent phase-matching OPAs or chirped-pulse OPAs, it should be promising to achieve intense femtosecond laser pulses that are close to the diffraction limit in space and ultra-high contrast in time, simultaneously.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61222509 and 11421064)the W.M.Keck Foundation
文摘Ultrashort multi-ke V x-ray pulses are generated by electron plasma produced by the irradiation of femtosecond pulses on metals. These sub-picosecond x-ray pulses have extended the field of x-ray spectroscopy into the femtosecond time domain. However, pulse-to-pulse instability and long data acquisition time restrict the application of ultrashort x-ray systems operating at low repetition rates. Here we report on the performance of a femtosecond laser plasma-induced hard x-ray source that operates at 1-k Hz repetition rate, and provides a flux of 2.0 × 10^10 photons/s of Cu Kαradiation. Using this system for time-resolved x-ray diffraction experiments, we record in real time, the transient processes and structural changes induced by the interaction of 400-nm femtosecond pulse with the surface of a 200-nm thick Au(111) single crystal.