Jianmin Yuan Yuan - Academia.edu (original) (raw)
Papers by Jianmin Yuan Yuan
Physical Review A, 2015
We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort f... more We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort fundamental laser and its second harmonic field by solving time-dependent Schrödinger equation (TDSE). The comparisons between one-, two-, and three-dimensional TDSE numerical simulations show that initial ionized wave-packet and its subsequent acceleration in the laser field and rescattering with long-range Coulomb potential play key roles. We also present the dependence of the optimum phase delay and yield of terahertz radiation on the laser intensity, wavelength, duration, and the ratio of two-color laser components. Terahertz wave generation from model hydrogen molecules are further investigated by comparing with high harmonic emission. It is found that the terahertz yield is following the alignment dependence of ionization rate, while the optimal two-color phase delays varies by a small amount when the alignment angle changes from 0 to 90 degrees, which reflects alignment dependence of attosecond electron dynamics. Finally we show that terahertz emission might be used to clarify the origin of interference in high harmonic generation from aligned molecules by coincidently measuring the angle-resolved THz yields.
Physical Review E
The thermodynamic as well as optical properties of strongly coupled plasmas depend crucially on t... more The thermodynamic as well as optical properties of strongly coupled plasmas depend crucially on the average degree of ionization and the ionic state composition, which, however, cannot be determined by using the normal Saha equation usually used for the ideal plasmas. Hence, an adequate treatment of the ionization balance and the charge state distribution of strongly coupled plasmas is still a challenge for theory due to the interactions between the electrons and ions and among the electrons themselves. Based on a local density temperature-dependent ionsphere model, the Saha equation approach is extended to the regime of strongly coupled plasmas by taking into account the free-electron-ion interaction, the free-free-electron interaction, the nonuniform free-electron space distribution, and the free-electron quantum partial degeneracy. All the quantities, including the bound orbitals with ionization potential depression, free-electron distribution, and bound and free-electron partition function contributions, are calculated self-consistently in the theoretical formalism. This study shows that the ionization equilibrium is evidently modified by considering the above nonideal characteristics of the free electrons. Our theoretical formalism is validated by the explanation of a recent experimental measurement of the opacity of dense hydrocarbon.
Physical Review A
Molecular dimers have attracted much attention in the study of molecular structure and dynamics d... more Molecular dimers have attracted much attention in the study of molecular structure and dynamics due to their complex interactions involving both weak van der Waals and strong covalent bonds. We investigate the dissociative ionization of carbon dioxide dimers exposed to intense femtosecond laser fields. The angular distributions of ionic fragments of the breakup channels (CO 2) 2 2+ → CO 2 + + CO 2 + and (CO 2) 2 3+ → CO 2 2+ + CO 2 + strongly depend on the laser intensity. Simulations based on time-dependent density-functional theory reproduce the experimental observations qualitatively and show that the angular distribution of fragments is determined by the angle-dependent orbital ionization probability and the relative contributions of different orbitals, both of which are intensity sensitive. By comparing the ionization of the dimer with CO 2 monomer, we find that the weak van der Waals bond and molecular geometry in the dimer play considerable roles. This work extends significantly earlier studies of simple linear covalent bond molecules.
arXiv (Cornell University), Apr 10, 2022
Light-matter interaction is exploited in spectroscopic techniques to access information about mol... more Light-matter interaction is exploited in spectroscopic techniques to access information about molecular, atomic or nuclear constituents of the sample of interest. While scattered light carries both amplitude and phase information of
Communications Physics, 2018
Continuum atomic processes initiated by photons and electrons occurring in a plasma are fundament... more Continuum atomic processes initiated by photons and electrons occurring in a plasma are fundamental in plasma physics, playing a key role in the determination of ionization balance, equation of state, and opacity. Here we propose the notion of a transient space localization of electrons produced during the ionization of atoms immersed in a hot dense plasma, which can significantly modify the fundamental properties of ionization processes. A theoretical formalism is developed to study the wavefunctions of the continuum electrons that takes into consideration the quantum de-coherence caused by coupling with the plasma environment. The method is applied to the photoionization of Fe16+ embedded in hot dense plasmas. We find that the cross section is considerably enhanced compared with the predictions of the existing isolated-atom model, and thereby partly explains the big difference between the measured opacity of Fe plasma and the existing standard models for short wavelengths.
Physics of Plasmas, 2015
Ionization competition arising from the electronic shell structures of various atomic species in ... more Ionization competition arising from the electronic shell structures of various atomic species in the mixture plasmas was investigated, taking SiO 2 as an example. Using a detailed-level-accounting approximation, we studied the competition effects on the charge state population distribution and spectrally resolved and Planck and Rosseland mean radiative opacities of mixture plasmas. A set of coupled equations for ionization equilibria that include all components of the mixture plasmas are solved to determine the population distributions. For a given plasma density, competition effects are found at three distinct temperature ranges, corresponding to the ionization of M-, Land nd K-shell electrons of Si. Taking the effects into account, the spectrally resolved and Planck and Rosseland mean opacities are systematically investigated over a wide range of plasma densities and temperatures. For a given mass density, the Rosseland mean decreases monotonically with plasma temperature, whereas Planck mean does not. Although the overall trend is a decrease, the Planck mean increases over a finite intermediate temperature regime. A comparison with the available experimental and theoretical results is made. V
Science China Physics, Mechanics & Astronomy, 2021
Physical Review E
An analytical self-consistent approach was recently established to predict the ionization potenti... more An analytical self-consistent approach was recently established to predict the ionization potential depression (IPD) in multicomponent dense plasmas, which is achieved by considering the self-energy of ions and electrons within the quantum statistical theory. In order to explicitly account for the exchange-correlation effect of electrons, we incorporate the effective static approximation of local field correction (LFC) within our IPD framework through the connection of dynamical structure factor. The effective static approximation poses an accurate description for the asymptotic large wave number behavior with the recently developed machine learning representation of static LFC induced from the path-integral Monte Carlo data. Our calculation shows that the introduction of static LFC through dynamical structure factor brings a nontrivial influence on IPD at warm/hot dense matter conditions. The correlation effect within static LFC could provide up to 20% correction to free-electron contribution of IPD in the strong coupling and degeneracy regime. Furthermore, a new screening factor is obtained from the density distribution of free electrons calculated within the average-atom model, with which excellent agreements are observed with other methods and experiments at warm/hot dense matter conditions.
To understand the dynamically-assisted Schwinger effect in a spatially inhomogeneous field, the t... more To understand the dynamically-assisted Schwinger effect in a spatially inhomogeneous field, the two-dimensional momentum distribution of the electron/positron created in an intense standing wave is computed in the non-perturbative regime. Characteristic structures of resonance rings are revealed which directly display multi-photon pair production channels. The particle's effective mass can be extracted from the resonance rings and an effective mass model is verified. In particular, featured breaks and distortion of the resonance rings are observed, which are proved to be an evidence of the band structure of the particle's energy in the standing wave. A general energy gap model applicable for various momentum conditions beyond previous analytical work is established and justified by recovering the resonance ring's distortion and also by comparing with the gap width directly extracted from the breaking points. The theoretical work is based on developed numerical methods an...
International Journal of Molecular Sciences
Recent experiments have observed much higher electron–ion collisional ionization cross sections a... more Recent experiments have observed much higher electron–ion collisional ionization cross sections and rates in dense plasmas than predicted by the current standard atomic collision theory, including the plasma screening effect. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe the dissipation that occurs during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in the partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of the electron–ion collisional ionization of ions in plasma compared to isolated ions. Here, we develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma ...
The current standard atomic collision theory cannot explain recent experiments on electron-ion co... more The current standard atomic collision theory cannot explain recent experiments on electron-ion collisional ionization processes in hot dense plasma. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe dissipation during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum-electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of electron-ion collisional ionization of ions in plasma compared with isolated ions. We develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma screening and transient spatial localization. The approach is then used to investigate electron-impact ioniza...
Astronomy & Astrophysics, 2020
Recent quantitative experiments on the ionization potential depression (IPD) in dense plasma show... more Recent quantitative experiments on the ionization potential depression (IPD) in dense plasma show that the observational results are difficult to explain with the widely used analytical models for plasma screening. Here, we investigate the effect of plasma screening on the IPD and ionization balance of dense carbon plasma under solar and stellar interior conditions using our developed consistent nonanalytical model. The screening potential can be primarily attributed to the free electrons in the plasma and is determined by the microspace distribution of these free electrons. The ionization balance is determined by solving the Saha equation, including the effect of IPD. The predicted IPD and average ionization degree are larger than those obtained using the Stewart–Pyatt model for mass densities that are greater than 3.0 g cm−3. Under solar interior conditions, our results are in better agreement with the Ecker–Kröll model at electron temperatures and densities lower than 250 eV and ...
Physical Review A, May 30, 2019
Exchange correlation plays an important role in double-ionization of complex atoms by ultrashort ... more Exchange correlation plays an important role in double-ionization of complex atoms by ultrashort laser pulse. In this work, we investigate two-photon double inner-shell electron ionization of neon induced by an attosecond extreme ultraviolent pulse in the framework of the quantum master equation. Our simulations reveal a distinct non-sequential effect via broadened double peaks, as a result of energy sharing between the two ionized electrons. When dissipation is included to show the interplay of coherence and decoherence, the two-photon double-ionization scaling law breaks down. We further study the total cross section of 2s 2 double ionization as a function of photon energy in both non-sequential and sequential regions.
We perform a joint measurement of terahertz waves and high-order harmonics generated from noble a... more We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.
Nuclear quantum effects (NQEs) on the structures and transport properties of dense liquid hydroge... more Nuclear quantum effects (NQEs) on the structures and transport properties of dense liquid hydrogen at densities of 10-100 g/cm3 and temperatures of 0.1-1 eV are fully assessed using ab initio path-integral molecular dynamics simulations. With the inclusion of NQEs, ionic diffusions are strongly enhanced by the magnitude from 100 conductivities are significantly suppressed. The analyses of ionic structures and zero-point energy show also the importance of NQEs in these regime. The significant quantum delocalization of ions introduces expressively different scattering cross section between protons compared with classical particle treatments, which can explain the large alterability of transport behaviors. Furthermore, the energy, pressure, and isotope effects are also greatly influenced by NQEs. The complex behaviors show that NQEs can not be neglected for dense hydrogen even in the warm dense regime.
Physical Review A, 2021
Molecular spectroscopy is a powerful tool for accelerating advances in materials science, chemist... more Molecular spectroscopy is a powerful tool for accelerating advances in materials science, chemistry, biology, and astronomy. Typically, molecular spectroscopy uses nanotips or nanoparticles to locally detect the molecule properties in a sample resulting from absorption of infrared and terahertz radiations. Here, we present an alternative that transient localized plasma can be applied to enhance the molecular spectroscopy. Our experiments show a significant enhancement of rotational transitions in carbon monoxide plasma under the illumination of terahertz waves. We proposed a semiclassical model for this enhancement, dominated by the energy exchange from electrons to molecules or ions via a collision process in the localized plasma. Our findings gain more insight into the nonequilibrium dynamics in laser-generated localized plasma. We also propose that the localized plasma can be used to improve the sensitivity of molecular spectroscopy.
A generalization of non-perturbative QED model for high harmonic generation is developed for the ... more A generalization of non-perturbative QED model for high harmonic generation is developed for the multi-mode optical field case. By introducing classical-field-dressed quantized Volkov states analytically, a formula to calculate HHG for hydrogen-like atom in ultrashort intense laser pulse is obtained, which has a simple intuitive interpretation. The dressed state QED model indicates a new perspective to understand HHG, for example, the presence of the weak even-order harmonic photons, which has been verified by both theoretical analysis and numerical computation. Long wavelength approximation and strong field approximation are involved in the development of the formalism.
The complex structures of warm and hot dense matter are essential to understand the behaviors of ... more The complex structures of warm and hot dense matter are essential to understand the behaviors of materials in high energy density physics processes and provide new features of matter constitutions. Here, along a new unified first-principle determined Hugoniot curve of iron from normal condensed condition up to 1 Gbar, the novel structures characterized by the ionic clusters and separated "electron bubbles" are revolutionarily unraveled using newly developed quantum Langevin molecular dynamics (QLMD). Subsistence of complex clusters, with bonds formed by inner shell electrons of neighbor ions, can persist in the time length of 50 femto-seconds dynamically with quantum flowing bubbles, which are produced by the interplay of Fermi electron degeneracy, the ionic coupling and the dynamical nature. With the inclusion of those complicated features in QLMD, the present data could serve as a first-principle benchmark in a wide range of temperatures and densities.
Scientific reports, Jan 2, 2014
We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with con... more We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with continuous variables (CV). This system employs coherent light pulses and time multiplexing to maximally reduce cross talk in the fiber. No-switching detection scheme is adopted to optimize the repetition rate. Information is encoded on the sideband of the pulsed coherent light to fully exploit the continuous wave nature of laser field. With this configuration, high secret key rate can be achieved. For the 50 MHz detected bandwidth in our experiment, when the multidimensional reconciliation protocol is applied, a secret key rate of 187 kb/s can be achieved over 50 km of optical fiber against collective attacks, which have been shown to be asymptotically optimal. Moreover, recently studied loopholes have been fixed in our system.
The equation of state (EOS) of the solar interior is accurately and smoothly determined from ab i... more The equation of state (EOS) of the solar interior is accurately and smoothly determined from ab initio simulations named quantum Langevin molecular dynamics (QLMD) in the pressure range of 58 ≤ P ≤ 4.6 × 10 5 Mbar at the temperature range of 1 ≤ T ≤ 1500 eV. The central pressure is calculated, and compared with other models. The effect of heavy elements such as carbon and oxygen on the EOS is also discussed.
Physical Review A, 2015
We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort f... more We study the generation of terahertz radiation from atoms and molecules driven by an ultrashort fundamental laser and its second harmonic field by solving time-dependent Schrödinger equation (TDSE). The comparisons between one-, two-, and three-dimensional TDSE numerical simulations show that initial ionized wave-packet and its subsequent acceleration in the laser field and rescattering with long-range Coulomb potential play key roles. We also present the dependence of the optimum phase delay and yield of terahertz radiation on the laser intensity, wavelength, duration, and the ratio of two-color laser components. Terahertz wave generation from model hydrogen molecules are further investigated by comparing with high harmonic emission. It is found that the terahertz yield is following the alignment dependence of ionization rate, while the optimal two-color phase delays varies by a small amount when the alignment angle changes from 0 to 90 degrees, which reflects alignment dependence of attosecond electron dynamics. Finally we show that terahertz emission might be used to clarify the origin of interference in high harmonic generation from aligned molecules by coincidently measuring the angle-resolved THz yields.
Physical Review E
The thermodynamic as well as optical properties of strongly coupled plasmas depend crucially on t... more The thermodynamic as well as optical properties of strongly coupled plasmas depend crucially on the average degree of ionization and the ionic state composition, which, however, cannot be determined by using the normal Saha equation usually used for the ideal plasmas. Hence, an adequate treatment of the ionization balance and the charge state distribution of strongly coupled plasmas is still a challenge for theory due to the interactions between the electrons and ions and among the electrons themselves. Based on a local density temperature-dependent ionsphere model, the Saha equation approach is extended to the regime of strongly coupled plasmas by taking into account the free-electron-ion interaction, the free-free-electron interaction, the nonuniform free-electron space distribution, and the free-electron quantum partial degeneracy. All the quantities, including the bound orbitals with ionization potential depression, free-electron distribution, and bound and free-electron partition function contributions, are calculated self-consistently in the theoretical formalism. This study shows that the ionization equilibrium is evidently modified by considering the above nonideal characteristics of the free electrons. Our theoretical formalism is validated by the explanation of a recent experimental measurement of the opacity of dense hydrocarbon.
Physical Review A
Molecular dimers have attracted much attention in the study of molecular structure and dynamics d... more Molecular dimers have attracted much attention in the study of molecular structure and dynamics due to their complex interactions involving both weak van der Waals and strong covalent bonds. We investigate the dissociative ionization of carbon dioxide dimers exposed to intense femtosecond laser fields. The angular distributions of ionic fragments of the breakup channels (CO 2) 2 2+ → CO 2 + + CO 2 + and (CO 2) 2 3+ → CO 2 2+ + CO 2 + strongly depend on the laser intensity. Simulations based on time-dependent density-functional theory reproduce the experimental observations qualitatively and show that the angular distribution of fragments is determined by the angle-dependent orbital ionization probability and the relative contributions of different orbitals, both of which are intensity sensitive. By comparing the ionization of the dimer with CO 2 monomer, we find that the weak van der Waals bond and molecular geometry in the dimer play considerable roles. This work extends significantly earlier studies of simple linear covalent bond molecules.
arXiv (Cornell University), Apr 10, 2022
Light-matter interaction is exploited in spectroscopic techniques to access information about mol... more Light-matter interaction is exploited in spectroscopic techniques to access information about molecular, atomic or nuclear constituents of the sample of interest. While scattered light carries both amplitude and phase information of
Communications Physics, 2018
Continuum atomic processes initiated by photons and electrons occurring in a plasma are fundament... more Continuum atomic processes initiated by photons and electrons occurring in a plasma are fundamental in plasma physics, playing a key role in the determination of ionization balance, equation of state, and opacity. Here we propose the notion of a transient space localization of electrons produced during the ionization of atoms immersed in a hot dense plasma, which can significantly modify the fundamental properties of ionization processes. A theoretical formalism is developed to study the wavefunctions of the continuum electrons that takes into consideration the quantum de-coherence caused by coupling with the plasma environment. The method is applied to the photoionization of Fe16+ embedded in hot dense plasmas. We find that the cross section is considerably enhanced compared with the predictions of the existing isolated-atom model, and thereby partly explains the big difference between the measured opacity of Fe plasma and the existing standard models for short wavelengths.
Physics of Plasmas, 2015
Ionization competition arising from the electronic shell structures of various atomic species in ... more Ionization competition arising from the electronic shell structures of various atomic species in the mixture plasmas was investigated, taking SiO 2 as an example. Using a detailed-level-accounting approximation, we studied the competition effects on the charge state population distribution and spectrally resolved and Planck and Rosseland mean radiative opacities of mixture plasmas. A set of coupled equations for ionization equilibria that include all components of the mixture plasmas are solved to determine the population distributions. For a given plasma density, competition effects are found at three distinct temperature ranges, corresponding to the ionization of M-, Land nd K-shell electrons of Si. Taking the effects into account, the spectrally resolved and Planck and Rosseland mean opacities are systematically investigated over a wide range of plasma densities and temperatures. For a given mass density, the Rosseland mean decreases monotonically with plasma temperature, whereas Planck mean does not. Although the overall trend is a decrease, the Planck mean increases over a finite intermediate temperature regime. A comparison with the available experimental and theoretical results is made. V
Science China Physics, Mechanics & Astronomy, 2021
Physical Review E
An analytical self-consistent approach was recently established to predict the ionization potenti... more An analytical self-consistent approach was recently established to predict the ionization potential depression (IPD) in multicomponent dense plasmas, which is achieved by considering the self-energy of ions and electrons within the quantum statistical theory. In order to explicitly account for the exchange-correlation effect of electrons, we incorporate the effective static approximation of local field correction (LFC) within our IPD framework through the connection of dynamical structure factor. The effective static approximation poses an accurate description for the asymptotic large wave number behavior with the recently developed machine learning representation of static LFC induced from the path-integral Monte Carlo data. Our calculation shows that the introduction of static LFC through dynamical structure factor brings a nontrivial influence on IPD at warm/hot dense matter conditions. The correlation effect within static LFC could provide up to 20% correction to free-electron contribution of IPD in the strong coupling and degeneracy regime. Furthermore, a new screening factor is obtained from the density distribution of free electrons calculated within the average-atom model, with which excellent agreements are observed with other methods and experiments at warm/hot dense matter conditions.
To understand the dynamically-assisted Schwinger effect in a spatially inhomogeneous field, the t... more To understand the dynamically-assisted Schwinger effect in a spatially inhomogeneous field, the two-dimensional momentum distribution of the electron/positron created in an intense standing wave is computed in the non-perturbative regime. Characteristic structures of resonance rings are revealed which directly display multi-photon pair production channels. The particle's effective mass can be extracted from the resonance rings and an effective mass model is verified. In particular, featured breaks and distortion of the resonance rings are observed, which are proved to be an evidence of the band structure of the particle's energy in the standing wave. A general energy gap model applicable for various momentum conditions beyond previous analytical work is established and justified by recovering the resonance ring's distortion and also by comparing with the gap width directly extracted from the breaking points. The theoretical work is based on developed numerical methods an...
International Journal of Molecular Sciences
Recent experiments have observed much higher electron–ion collisional ionization cross sections a... more Recent experiments have observed much higher electron–ion collisional ionization cross sections and rates in dense plasmas than predicted by the current standard atomic collision theory, including the plasma screening effect. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe the dissipation that occurs during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in the partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of the electron–ion collisional ionization of ions in plasma compared to isolated ions. Here, we develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma ...
The current standard atomic collision theory cannot explain recent experiments on electron-ion co... more The current standard atomic collision theory cannot explain recent experiments on electron-ion collisional ionization processes in hot dense plasma. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe dissipation during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum-electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of electron-ion collisional ionization of ions in plasma compared with isolated ions. We develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma screening and transient spatial localization. The approach is then used to investigate electron-impact ioniza...
Astronomy & Astrophysics, 2020
Recent quantitative experiments on the ionization potential depression (IPD) in dense plasma show... more Recent quantitative experiments on the ionization potential depression (IPD) in dense plasma show that the observational results are difficult to explain with the widely used analytical models for plasma screening. Here, we investigate the effect of plasma screening on the IPD and ionization balance of dense carbon plasma under solar and stellar interior conditions using our developed consistent nonanalytical model. The screening potential can be primarily attributed to the free electrons in the plasma and is determined by the microspace distribution of these free electrons. The ionization balance is determined by solving the Saha equation, including the effect of IPD. The predicted IPD and average ionization degree are larger than those obtained using the Stewart–Pyatt model for mass densities that are greater than 3.0 g cm−3. Under solar interior conditions, our results are in better agreement with the Ecker–Kröll model at electron temperatures and densities lower than 250 eV and ...
Physical Review A, May 30, 2019
Exchange correlation plays an important role in double-ionization of complex atoms by ultrashort ... more Exchange correlation plays an important role in double-ionization of complex atoms by ultrashort laser pulse. In this work, we investigate two-photon double inner-shell electron ionization of neon induced by an attosecond extreme ultraviolent pulse in the framework of the quantum master equation. Our simulations reveal a distinct non-sequential effect via broadened double peaks, as a result of energy sharing between the two ionized electrons. When dissipation is included to show the interplay of coherence and decoherence, the two-photon double-ionization scaling law breaks down. We further study the total cross section of 2s 2 double ionization as a function of photon energy in both non-sequential and sequential regions.
We perform a joint measurement of terahertz waves and high-order harmonics generated from noble a... more We perform a joint measurement of terahertz waves and high-order harmonics generated from noble atoms driven by a fundamental laser pulse and its second harmonic. By correlating their dependence on the phase-delay of the two pulses, we determine the generation of THz waves in tens of attoseconds precision. Compared with simulations and models, we find that the laser-assisted soft-collision of the electron wave packet with the atomic core plays a key role. It is demonstrated that the rescattering process, being indispensable in HHG processes, dominant THz wave generation as well but in a more elaborate way. The new finding might be helpful for the full characterization of the rescattering dynamics.
Nuclear quantum effects (NQEs) on the structures and transport properties of dense liquid hydroge... more Nuclear quantum effects (NQEs) on the structures and transport properties of dense liquid hydrogen at densities of 10-100 g/cm3 and temperatures of 0.1-1 eV are fully assessed using ab initio path-integral molecular dynamics simulations. With the inclusion of NQEs, ionic diffusions are strongly enhanced by the magnitude from 100 conductivities are significantly suppressed. The analyses of ionic structures and zero-point energy show also the importance of NQEs in these regime. The significant quantum delocalization of ions introduces expressively different scattering cross section between protons compared with classical particle treatments, which can explain the large alterability of transport behaviors. Furthermore, the energy, pressure, and isotope effects are also greatly influenced by NQEs. The complex behaviors show that NQEs can not be neglected for dense hydrogen even in the warm dense regime.
Physical Review A, 2021
Molecular spectroscopy is a powerful tool for accelerating advances in materials science, chemist... more Molecular spectroscopy is a powerful tool for accelerating advances in materials science, chemistry, biology, and astronomy. Typically, molecular spectroscopy uses nanotips or nanoparticles to locally detect the molecule properties in a sample resulting from absorption of infrared and terahertz radiations. Here, we present an alternative that transient localized plasma can be applied to enhance the molecular spectroscopy. Our experiments show a significant enhancement of rotational transitions in carbon monoxide plasma under the illumination of terahertz waves. We proposed a semiclassical model for this enhancement, dominated by the energy exchange from electrons to molecules or ions via a collision process in the localized plasma. Our findings gain more insight into the nonequilibrium dynamics in laser-generated localized plasma. We also propose that the localized plasma can be used to improve the sensitivity of molecular spectroscopy.
A generalization of non-perturbative QED model for high harmonic generation is developed for the ... more A generalization of non-perturbative QED model for high harmonic generation is developed for the multi-mode optical field case. By introducing classical-field-dressed quantized Volkov states analytically, a formula to calculate HHG for hydrogen-like atom in ultrashort intense laser pulse is obtained, which has a simple intuitive interpretation. The dressed state QED model indicates a new perspective to understand HHG, for example, the presence of the weak even-order harmonic photons, which has been verified by both theoretical analysis and numerical computation. Long wavelength approximation and strong field approximation are involved in the development of the formalism.
The complex structures of warm and hot dense matter are essential to understand the behaviors of ... more The complex structures of warm and hot dense matter are essential to understand the behaviors of materials in high energy density physics processes and provide new features of matter constitutions. Here, along a new unified first-principle determined Hugoniot curve of iron from normal condensed condition up to 1 Gbar, the novel structures characterized by the ionic clusters and separated "electron bubbles" are revolutionarily unraveled using newly developed quantum Langevin molecular dynamics (QLMD). Subsistence of complex clusters, with bonds formed by inner shell electrons of neighbor ions, can persist in the time length of 50 femto-seconds dynamically with quantum flowing bubbles, which are produced by the interplay of Fermi electron degeneracy, the ionic coupling and the dynamical nature. With the inclusion of those complicated features in QLMD, the present data could serve as a first-principle benchmark in a wide range of temperatures and densities.
Scientific reports, Jan 2, 2014
We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with con... more We report a fiber-based quasi-continuous-wave (CW) quantum key distribution (QKD) system with continuous variables (CV). This system employs coherent light pulses and time multiplexing to maximally reduce cross talk in the fiber. No-switching detection scheme is adopted to optimize the repetition rate. Information is encoded on the sideband of the pulsed coherent light to fully exploit the continuous wave nature of laser field. With this configuration, high secret key rate can be achieved. For the 50 MHz detected bandwidth in our experiment, when the multidimensional reconciliation protocol is applied, a secret key rate of 187 kb/s can be achieved over 50 km of optical fiber against collective attacks, which have been shown to be asymptotically optimal. Moreover, recently studied loopholes have been fixed in our system.
The equation of state (EOS) of the solar interior is accurately and smoothly determined from ab i... more The equation of state (EOS) of the solar interior is accurately and smoothly determined from ab initio simulations named quantum Langevin molecular dynamics (QLMD) in the pressure range of 58 ≤ P ≤ 4.6 × 10 5 Mbar at the temperature range of 1 ≤ T ≤ 1500 eV. The central pressure is calculated, and compared with other models. The effect of heavy elements such as carbon and oxygen on the EOS is also discussed.