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Jiaolong Zeng

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I am a physics researcher. My major is atomic and molecule physics and plasma physics. My current interests are atomic structure, ionization potential depression, ionization balance, and physical properties of opacity, equation of state of dense plasmas.

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University of Southern California

Manfred Grieser

Mofreh Zaghloul

Jianmin Yuan Yuan

Yuri Kurilenkov

Joint Institute for High Temperature

Alexander Potekhin

Ioffe Physical Technical Institute

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Papers by Jiaolong Zeng

Nonideal effect of free electrons on ionization equilibrium and radiative property in dense plasmas

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.

The Strong Enhancement of Electron-Impact Ionization Processes in Dense Plasma by Transient Spatial Localization

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 ...

Strong enhancement of electron-impact-ionization processes in hot dense plasma by transient spatial localization

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...

Enhancement of electron-impact ionization induced by warm dense environments

Physical Review E, 2021

Studies have shown significant discrepancies between the recent experiment [Berg et al., Phys. Re... more Studies have shown significant discrepancies between the recent experiment [Berg et al., Phys. Rev. Lett. 120, 055002 (2018)] and current theoretical calculations on the electron-impact ionization cross section of ions in warm dense magnesium. Here, we present a systematic study the effects of the ionic correlations and freeelectron screening on the electron-impact ionization of ions in warm dense matter. The ionic correlation and the free-electron screening effects yield additional Hermitian terms to the calculation of the ionic central-force-field potential, which significantly change the electronic structure compared with that of the isolated ion. In calculating the electron-impact ionization, we describe the impact and ionized electrons using a damped-distorted wave function, which considers the momentum relaxation of free electrons due to collisions with other free electrons and ions. We reproduce the electron-impact ionization process for Mg 7+ in the solid-density plasma and increase the ionization cross section by one order of magnitude compared with that of the isolated ion, which excellently agrees with the experimental result of Berg et al.

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

Astronomy & Astrophysics, 2020

An accurate description of the screening potential induced by a hot, dense plasma is a fundamenta... more An accurate description of the screening potential induced by a hot, dense plasma is a fundamental problem in atomic physics and plasma physics, and it plays a pivotal role in the investigation of microscopic atomic processes and the determination of macroscopic physical properties, such as opacities and equations of state as well as nuclear fusion cross sections. Recent experimental studies show that currently available analytical models of plasma screening have difficulty in accurately describing the ionization-potential depression, which is directly determined by the screening potential. Here, we propose a consistent approach to determine the screening potential in dense plasmas under solar-interior conditions from the free-electron micro-space distribution. It is assumed that the screening potential for an ion embedded in a dense plasma is predominately determined by the free electrons in the plasma. The free-electron density is obtained by solving the ionization-equilibrium equ...

Transient space localization of electrons ejected from continuum atomic processes in hot dense plasma

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.

Auger decay and the direct double ionization probability of a 2p inner-shell hole in a singly charged Ar+ ion

The European Physical Journal D, 2014

Single and double Auger decay processes of Ar + 2p −1 hole levels belonging to the configurations... more Single and double Auger decay processes of Ar + 2p −1 hole levels belonging to the configurations of 2p 5 3s 2 3p 5 and 2p 5 3s3p 6 are investigated in the framework of perturbation theory implemented by the distorted wave approximation. The single Auger decay channels and rates are determined and the predicted total rates can differ by more than an order of magnitude for the levels of 2p 5 3s 2 3p 5 , yet they are very close for levels belonging to 2p 5 3s3p 6. By combining the double photoionization cross sections of the neutral species, our theoretical Auger spectra of the single Auger decay process nicely interpreted a recent experiment [S.M. Huttula et al., Phys. Rev. Lett. 110, 113002 (2013)]. A configuration averaged branching ratio of 6.5% and 7.3% are predicted for the direct double Auger decay to the total probability for 2p 5 3s 2 3p 5 and 2p 5 3s3p 6 , respectively, which is smaller than that of Ar 2p −1 hole states.

Coherence and resonance effects in the ultra-intense laser-induced ultrafast response of complex atoms

Scientific reports, Jan 6, 2016

Both coherent pumping and energy relaxation play important roles in understanding physical proces... more Both coherent pumping and energy relaxation play important roles in understanding physical processes of ultra-intense coherent light-matter interactions. Here, using a large-scale quantum master equation approach, we describe dynamical processes of practical open quantum systems driven by both coherent and stochastic interactions. As examples, two typical cases of light-matter interactions are studied. First, we investigate coherent dynamics of inner-shell electrons of a neon gas irradiated by a high-intensity X-ray laser along with vast number of decaying channels. In these single-photon dominated processes, we find that, due to coherence-induced Rabi oscillations and power broadening effects, the photon absorptions of a neon gas can be suppressed resulting in differences in ionization processes and final ion-stage distributions. Second, we take helium as an example of multiphoton and multichannel interference dominated electron dynamics, by investigating the transient absorption o...

Double core-hole spectroscopy of transient plasmas produced in the interaction of ultraintense x-ray pulses with neon

Double core-hole (DCH) spectroscopy is investigated systematically for neon atomic system in the ... more Double core-hole (DCH) spectroscopy is investigated systematically for neon atomic system in the interaction with ultraintense x-ray pulses with photon energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in the detailed level accounting approximation, is utilized to study the dynamical evolution of the level population and emission properties of the highly transient plasmas. For x-ray pulses with photon energy in the range of 937-1030 eV, where 1s → 2p resonance absorption from single core-hole (SCH) states of neon charge states exist, inner-shell resonant absorption (IRA) effects play important roles in the time evolution of population and DCH spectroscopy. Such IRA physical effects are illustrated in detail by investigating the interaction of x-ray pulses at a photon energy of 944 eV, which corresponds to the 1s → 2p resonant absorption from the SCH states (1s2s 2 2p 4 , 1s2s2p 5 and 1s2p 6) of Ne 3+. After averaging over the space and time distribution of t...

Nuclear quantum dynamics in dense hydrogen

Scientific Reports, 2014

Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scatter... more Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scattering or many-body collisions between particles, is crucial for the dynamics of planet's evolution and hydrodynamical processes in inertial confinement confusion. Here, using improved ab initio path-integral molecular dynamics simulations, we investigated the nuclear quantum dynamics regarding transport behaviors of dense hydrogen up to the temperatures of 1 eV. With the inclusion of nuclear quantum effects (NQEs), the ionic diffusions are largely higher than the classical treatment by the magnitude from 20% to 146% as the temperature is decreased from 1 eV to 0.3 eV at 10 g/cm 3 , meanwhile, electrical and thermal conductivities are significantly lowered. In particular, the ionic diffusion is found much larger than that without NQEs even when both the ionic distributions are the same at 1 eV. The significant quantum delocalization of ions introduces remarkably different scattering cross section between protons compared with classical particle treatments, which explains the large difference of transport properties induced by NQEs. The Stokes-Einstein relation, Wiedemann-Franz law, and isotope effects are reexamined , showing different behaviors in nuclear quantum dynamics. N uclear quantum nature, especially for protons, manifests its significant effects on the ionic structures, phase diagram and ionic dynamics 1-5. A lot of researches focus on the nuclear quantum effects (NQEs) such as quantum fluctuations and zero-point motion on the structures of dense hydrogen 6-10 , revealing many intriguing physics. However, the nuclear quantum dynamics such as ionic quantum transport is rarely studied because of the computational and the theoretical challenges. Only at low temperatures, the nuclear quantum dynamics was investigated. For example, large deviation for ionic diffusion and thermal conductivity of para-hydrogen is found below 32 K induced by NQEs compared with the classical-particle treatment 11. At high temperatures, in particular in warm dense regime (i.e., above 1000 K), ions are usually considered as distinguishable classical particles by assuming the quantum fluctuations or quantum collisions are negligible. However, even for the collision energies up to 10 eV, it has been shown that elastic collision cross sections for protons and hydrogen atoms can be very different in the quantum and classical theory 12 , indicating the possible failure of classical treatment for nuclear motion in warm dense regime. Dense hydrogen plays a crucial role in understanding the material behaviors under extreme conditions 13,14 and has important applications in energy sources 15 and astrophysics 16,17. The associated ionic and electronic transport properties are the key to tracing the dynamics of capsule implosion of inertial confinement fusion (ICF) 15 , modeling plasma processes 18 and the interior structure and evolution of giant planets and exoplanets 19-21. More exact transport properties such as thermal conductivities and electron-ion relaxation rates are required because they can remarkably alter the dynamics of planet's evolution 22 and hydrodynamical processes in ICF 23. The core pressures of some newly discovered exoplanets are estimated even up to 19 Gbar 21 , while the temperature may be several thousand Kelvins. Thanks to the recent progress in experimental techniques, one could get access to this previously inaccessible regime of phase diagram of hydrogen through a laser-induced shock wave loading of precompressed samples 24,25. However, theoretically understanding the nature of hydrogen under the ultra-high pressures is still rare and a great challenge. Density functional theory based ab initio molecular dynamics (MD) has been widely used to investigate transport properties such as ionic diffusion, electrical conductivity of dense matter at high temperatures 26-28. In viewpoint of collision physics, both the ionic and electronic transport properties depend strongly on the scattering cross sections between particles. In usual ab initio MD simulations, the corresponding scattering cross sections are statistically obtained from classical particle

Detailed-term-accounting-approximation simulation of x-ray transmission through laser-produced Al plasmas

Physical Review E, 2000

An extensive configuration interaction ͑CI͒ scheme and the R-matrix method are combined to calcul... more An extensive configuration interaction ͑CI͒ scheme and the R-matrix method are combined to calculate the x-ray transmission spectrum for high-power laser-produced Al plasmas in local thermodynamic equilibrium by using the detailed-term-accounting ͑DTA͒ approximation. All atomic parameters such as state levels and photoabsorption cross sections for different ionization stages are obtained by using the CI and R-matrix method. Special attention is given to the effects of autoionizing resonance broadening on the transmission. A large difference exists between the convergence of the results with and without taking account of autoionizing resonance broadening when the autoionization resonance broadening is the major broadening mechanism. This shows that autoionizing resonance widths of the K-shell excited states have large effects and should be considered to interpret the spectral-resolved transmission.

Radiative opacities and configuration interaction effects of hot iron plasma using a detailed term accounting model

Physical Review E, 2003

We have calculated the radiative opacities of iron plasma in local thermodynamic equilibrium usin... more We have calculated the radiative opacities of iron plasma in local thermodynamic equilibrium using a detailed term accounting model. The extensive atomic data are obtained by multiconfiguration Hartree-Fock ͑MCHF͒ method, with Breit-Pauli relativistic corrections. Extensive configuration interaction ͑CI͒ has been included based on LS coupling to obtain energy levels and the bound-bound transition cross sections. A detailed configuration accounting model is applied to evaluate the bound-free absorption cross sections. We simulate two experimental transmission spectra ͓G.

Detailed-term-accounting approximation calculations of the radiative opacity of aluminum plasmas: A systematic study

Physical Review E, 2002

The spectrally resolved radiative opacity and the Rosseland and Planck mean opacities are calcula... more The spectrally resolved radiative opacity and the Rosseland and Planck mean opacities are calculated by using the detailed-term-accounting approximation for aluminum plasmas with varieties of density and temperature. The results are presented along a 40 eV isothermal sequence, a 0.01 g/cm 3 isodense sequence, and a sequence with average ionization degree Z*ϳ7.13. Particular attention is given to the influence of the detailed treatment of spectral lines on the Rosseland mean opacity under different thermodynamical conditions. The results show that at densities of 0.004 g/cm 3 and higher, the opacities are not very sensitive to the spectral linewidth within a reasonable range. As examples, the Rosseland mean opacity, which is most sensitive to the detailed linewidth, at 40 eV and 0.004 g/cm 3 changes no more than 15%, when we change the electron impact spectral linewidth artificially by reducing it by 50% or increasing it twice, and at 40 eV and 0.1 g/cm 3 it changes less than 5%. For comparison, we also carried out calculations by using an average atom model. For the Rosseland mean opacities, the two models show quite large differences, in particular at low densities, while for the Planck mean opacities the results of the two models are much closer.

Spectrally resolved opacities and Rosseland and Planck mean opacities of lowly ionized gold plasmas: A detailed level-accounting investigation

Physical Review E, 2007

Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fu... more Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fully relativistic detailed level-accounting approach are presented to show the importance of accurate atomic data for a quantitative reproduction of the experimental observations. Even though a huge number of transition lines are involved in the radiative absorption of high-Z plasmas so that one believes that statistical models can often give a reasonable description of their opacities, we first show in detail that an adequate treatment of physical effects, in particular the configuration interaction ͑including the core-valence electron correlation͒, is essential to produce atomic data of bound-bound and bound-free processes for gold plasmas, which are accurate enough to correctly explain the relative intensity of two strong absorption peaks experimentally observed located near photon energy of 70 and 80 eV. A detailed study is also carried out for gold plasmas of an average ionization degree sequence of 10, for both spectrally resolved opacities and Rosseland and Planck means. For comparison, results obtained by using an average atom model are also given to show that even for a relatively higher density of matter, correlation effects are also important to predict the correct positions of absorption peaks of transition arrays.

Radiative opacity of gold plasmas studied by a detailed level-accounting method

Physical Review E, 2006

There are systematic discrepancies unexplained so far between theory and experiment for opacities... more There are systematic discrepancies unexplained so far between theory and experiment for opacities of midand high-Z plasmas. To address this issue, we investigated the radiative opacity of gold plasmas by using a detailed level-accounting ͑DLA͒ method, in which various physical effects can be taken into account. In this work, we studied in detail the effects of core-valence electron correlation and linewidth on the opacity of gold plasmas. Our DLA results correctly explain the relative intensity of the two strong absorption peaks located near the photon energies of 70 and 80 eV, which was experimentally observed by Eidmann et al. ͓Europhys. Lett. 44, 459 ͑1998͔͒. Meanwhile, the DLA results showed that effects of saturation for the strong individual lines are evident in the transmission spectrum.

Detailed investigations on radiative opacity and emissivity of tin plasmas in the extreme-ultraviolet region

Physical Review E, 2010

Radiative opacity and emissivity of tin plasmas at average ionization degree of about 10 was inve... more Radiative opacity and emissivity of tin plasmas at average ionization degree of about 10 was investigated in detail by using a fully relativistic detailed level accounting approach, in which main physical effects on the opacity were carefully taken into account. Among these physical effects, configuration interaction, in particular core-valence electron correlations, plays an important role on the determination of accurate atomic data required in the calculation of opacity. It results in a strong narrowing of lines from all transition arrays and strong absorption is located in a narrow wavelength region of 12.5-14 nm for Sn plasmas. Using a complete accurate atomic data, we investigated the opacity of Sn plasmas at a variety of physical condition. Among the respective ions of Xe 6+-Xe 15+ , Xe 10+ has the largest absorption cross section at 13.5 nm, while the favorable physical condition for maximal absorption at 13.5 nm do not mean that Xe 10+ has the largest fraction. Comparison with other theoretical results showed that a complete set of consistent accurate atomic data, which lacks very much, is essential to predict accurate opacity. Our atomic model is useful and can be applied to interpret opacity experiments. Further benchmark experiments are urgently needed to clarify the physical effects on the opacity of Sn plasmas.

Photoionization for the ground state of Al VII from threshold to the K shell

Physical Review A, 2001

The photoionization cross sections of N-like Al VII are calculated from the first ionization thre... more The photoionization cross sections of N-like Al VII are calculated from the first ionization threshold to 140 Ry using the R-matrix method. 14 target states ͑including 4 K-shell excited states͒ of Al VIII are included in the close-coupling calculation. The detailed structure and resonances of the cross sections across the L-shell and K-shell thresholds is described. The resonance energies and widths of some of the autoionization states are determined by analyzing the resonance structures. The results show that the autoionization width of the K-shell excited state of a 1s electron being excited into 2p orbital is the largest among all of the autoionization states. It is also larger than Doppler and Stark widths under a typical plasma condition. This result shows that the autoionization widths will have essential influence in simulating the x-ray transmission spectrum of Al plasma.

Photodetachments of the metastablensnp24Pstates ofBe−,Mg−,andCa−ions

Physical Review A, 2000

Close-coupling calculations are performed on the photodetachments of the metastable nsnp 2 4 P st... more Close-coupling calculations are performed on the photodetachments of the metastable nsnp 2 4 P states of the negative beryllium (nϭ2), magnesium (nϭ3), and calcium (nϭ4) ions by using the R-matrix method. The calculations are carried out with the consideration of excitations of one electron from core. The results show that this effect is much more important for Ca Ϫ than for Be Ϫ and Mg Ϫ. For Be Ϫ , the total and partial cross sections are obtained from the threshold to a photon energy of 0.5 Ry. The calculated total cross section exhibits two 4 P o Feshbach resonances and one 4 D o shape resonance. Close agreement is found with the available theoretical calculations and the only experimental datum of Pegg and co-workers ͓Phys. Rev. A 50, 3861 ͑1994͔͒. For the Ca Ϫ and Mg Ϫ ions, the total and partial cross sections are calculated from the threshold to a photon energy of 0.25 Ry. For the Ca Ϫ ion, the resonances are found for both 4 P o and 4 D o symmetries just below the 3 D threshold. For the M g Ϫ ion, only a 4 P o resonance is predicted. No rapid increase associated with the opening of the 4s5s 3 S channel is found in the total cross section of Ca Ϫ. The rapid increase of the photodetachment cross section of Ca Ϫ in the experiment by Hanstorp et al. ͓D. Hanstorp et al., Phys. Rev. Lett. 63, 368 ͑1989͔͒ should not be attributed to the Ca Ϫ (4s4p 2 4 P)ϩh→Ca(4s5s 3 S)ϩkp ionization process. This result is consistent with the conclusion of Petrunin and co-workers ͓Phys. Rev. Lett. 76, 744 ͑1996͔͒ that there was no Ca Ϫ (4s4p 2 4 P) ions observed by Hanstorp et al.

Level-to-level and total probability for Auger decay including direct double processes of Ar2p−1hole states

Physical Review A, 2013

Auger decay including direct double processes of Ar 2p −1 hole levels is investigated in the fram... more Auger decay including direct double processes of Ar 2p −1 hole levels is investigated in the framework of perturbation theory implemented by distorted wave approximation with balanced large-scale configuration interaction among the successive ions being taken into account. The complex transition amplitude obtained from the second perturbation theory for the direct double Auger decay (DAD) is decomposed into approximate formulas according to two generally agreed mechanisms of shake-off and knockout. Practical computations showed that the knockout condition is fulfilled and thus justified such a decomposition treatment of knockout mechanism. The contribution to the DAD probability from knockout mechanism is larger than shake-off by an order of magnitude and therefore the former is dominant. The interference effect between the knockout and shake-off mechanisms should be trivial and neglecting it we obtained a branching ratio of 12.0% for the direct DAD into triply charged states of Ar 3+. By including cascade double decay, a total branching ratio of 14.9% is obtained. Our result explained recent experimental results on the branching ratio into triply charged ion, and should be useful for further detailed experimental investigations.

Inner-shell resonant absorption effects on evolution dynamics of the charge state distribution in a neon atom interacting with ultraintense x-ray pulses

Physical Review A, 2012

Inner-shell resonant absorption (IRA) effects were investigated on evolution dynamics of charge s... more Inner-shell resonant absorption (IRA) effects were investigated on evolution dynamics of charge state distribution (CSD) in the interaction of ultraintense x-ray pulses with a neon atom. IRA is the physical origin of the large discrepancies found between theory and experiment at a photon energy of 1050 eV [L. Young et al., Nature (London) 466, 56 (2010)], where the rates of K-shell resonant absorption 1s → 4p of Ne 6+ and 1s → 3p of Ne 7+ are larger than the direct single-photon ionization rates by more than one order of magnitude, and hence IRA becomes the dominant absorption mechanism. Only when the IRA effects are properly taken into account can we correctly explain the observed CSD.

Nonideal effect of free electrons on ionization equilibrium and radiative property in dense plasmas

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.

The Strong Enhancement of Electron-Impact Ionization Processes in Dense Plasma by Transient Spatial Localization

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 ...

Strong enhancement of electron-impact-ionization processes in hot dense plasma by transient spatial localization

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...

Enhancement of electron-impact ionization induced by warm dense environments

Physical Review E, 2021

Studies have shown significant discrepancies between the recent experiment [Berg et al., Phys. Re... more Studies have shown significant discrepancies between the recent experiment [Berg et al., Phys. Rev. Lett. 120, 055002 (2018)] and current theoretical calculations on the electron-impact ionization cross section of ions in warm dense magnesium. Here, we present a systematic study the effects of the ionic correlations and freeelectron screening on the electron-impact ionization of ions in warm dense matter. The ionic correlation and the free-electron screening effects yield additional Hermitian terms to the calculation of the ionic central-force-field potential, which significantly change the electronic structure compared with that of the isolated ion. In calculating the electron-impact ionization, we describe the impact and ionized electrons using a damped-distorted wave function, which considers the momentum relaxation of free electrons due to collisions with other free electrons and ions. We reproduce the electron-impact ionization process for Mg 7+ in the solid-density plasma and increase the ionization cross section by one order of magnitude compared with that of the isolated ion, which excellently agrees with the experimental result of Berg et al.

Screening potential and continuum lowering in a dense plasma under solar-interior conditions

Astronomy & Astrophysics, 2020

An accurate description of the screening potential induced by a hot, dense plasma is a fundamenta... more An accurate description of the screening potential induced by a hot, dense plasma is a fundamental problem in atomic physics and plasma physics, and it plays a pivotal role in the investigation of microscopic atomic processes and the determination of macroscopic physical properties, such as opacities and equations of state as well as nuclear fusion cross sections. Recent experimental studies show that currently available analytical models of plasma screening have difficulty in accurately describing the ionization-potential depression, which is directly determined by the screening potential. Here, we propose a consistent approach to determine the screening potential in dense plasmas under solar-interior conditions from the free-electron micro-space distribution. It is assumed that the screening potential for an ion embedded in a dense plasma is predominately determined by the free electrons in the plasma. The free-electron density is obtained by solving the ionization-equilibrium equ...

Transient space localization of electrons ejected from continuum atomic processes in hot dense plasma

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.

Auger decay and the direct double ionization probability of a 2p inner-shell hole in a singly charged Ar+ ion

The European Physical Journal D, 2014

Single and double Auger decay processes of Ar + 2p −1 hole levels belonging to the configurations... more Single and double Auger decay processes of Ar + 2p −1 hole levels belonging to the configurations of 2p 5 3s 2 3p 5 and 2p 5 3s3p 6 are investigated in the framework of perturbation theory implemented by the distorted wave approximation. The single Auger decay channels and rates are determined and the predicted total rates can differ by more than an order of magnitude for the levels of 2p 5 3s 2 3p 5 , yet they are very close for levels belonging to 2p 5 3s3p 6. By combining the double photoionization cross sections of the neutral species, our theoretical Auger spectra of the single Auger decay process nicely interpreted a recent experiment [S.M. Huttula et al., Phys. Rev. Lett. 110, 113002 (2013)]. A configuration averaged branching ratio of 6.5% and 7.3% are predicted for the direct double Auger decay to the total probability for 2p 5 3s 2 3p 5 and 2p 5 3s3p 6 , respectively, which is smaller than that of Ar 2p −1 hole states.

Coherence and resonance effects in the ultra-intense laser-induced ultrafast response of complex atoms

Scientific reports, Jan 6, 2016

Both coherent pumping and energy relaxation play important roles in understanding physical proces... more Both coherent pumping and energy relaxation play important roles in understanding physical processes of ultra-intense coherent light-matter interactions. Here, using a large-scale quantum master equation approach, we describe dynamical processes of practical open quantum systems driven by both coherent and stochastic interactions. As examples, two typical cases of light-matter interactions are studied. First, we investigate coherent dynamics of inner-shell electrons of a neon gas irradiated by a high-intensity X-ray laser along with vast number of decaying channels. In these single-photon dominated processes, we find that, due to coherence-induced Rabi oscillations and power broadening effects, the photon absorptions of a neon gas can be suppressed resulting in differences in ionization processes and final ion-stage distributions. Second, we take helium as an example of multiphoton and multichannel interference dominated electron dynamics, by investigating the transient absorption o...

Double core-hole spectroscopy of transient plasmas produced in the interaction of ultraintense x-ray pulses with neon

Double core-hole (DCH) spectroscopy is investigated systematically for neon atomic system in the ... more Double core-hole (DCH) spectroscopy is investigated systematically for neon atomic system in the interaction with ultraintense x-ray pulses with photon energy from 937 eV to 2000 eV. A time-dependent rate equation, implemented in the detailed level accounting approximation, is utilized to study the dynamical evolution of the level population and emission properties of the highly transient plasmas. For x-ray pulses with photon energy in the range of 937-1030 eV, where 1s → 2p resonance absorption from single core-hole (SCH) states of neon charge states exist, inner-shell resonant absorption (IRA) effects play important roles in the time evolution of population and DCH spectroscopy. Such IRA physical effects are illustrated in detail by investigating the interaction of x-ray pulses at a photon energy of 944 eV, which corresponds to the 1s → 2p resonant absorption from the SCH states (1s2s 2 2p 4 , 1s2s2p 5 and 1s2p 6) of Ne 3+. After averaging over the space and time distribution of t...

Nuclear quantum dynamics in dense hydrogen

Scientific Reports, 2014

Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scatter... more Nuclear dynamics in dense hydrogen, which is determined by the key physics of large-angle scattering or many-body collisions between particles, is crucial for the dynamics of planet's evolution and hydrodynamical processes in inertial confinement confusion. Here, using improved ab initio path-integral molecular dynamics simulations, we investigated the nuclear quantum dynamics regarding transport behaviors of dense hydrogen up to the temperatures of 1 eV. With the inclusion of nuclear quantum effects (NQEs), the ionic diffusions are largely higher than the classical treatment by the magnitude from 20% to 146% as the temperature is decreased from 1 eV to 0.3 eV at 10 g/cm 3 , meanwhile, electrical and thermal conductivities are significantly lowered. In particular, the ionic diffusion is found much larger than that without NQEs even when both the ionic distributions are the same at 1 eV. The significant quantum delocalization of ions introduces remarkably different scattering cross section between protons compared with classical particle treatments, which explains the large difference of transport properties induced by NQEs. The Stokes-Einstein relation, Wiedemann-Franz law, and isotope effects are reexamined , showing different behaviors in nuclear quantum dynamics. N uclear quantum nature, especially for protons, manifests its significant effects on the ionic structures, phase diagram and ionic dynamics 1-5. A lot of researches focus on the nuclear quantum effects (NQEs) such as quantum fluctuations and zero-point motion on the structures of dense hydrogen 6-10 , revealing many intriguing physics. However, the nuclear quantum dynamics such as ionic quantum transport is rarely studied because of the computational and the theoretical challenges. Only at low temperatures, the nuclear quantum dynamics was investigated. For example, large deviation for ionic diffusion and thermal conductivity of para-hydrogen is found below 32 K induced by NQEs compared with the classical-particle treatment 11. At high temperatures, in particular in warm dense regime (i.e., above 1000 K), ions are usually considered as distinguishable classical particles by assuming the quantum fluctuations or quantum collisions are negligible. However, even for the collision energies up to 10 eV, it has been shown that elastic collision cross sections for protons and hydrogen atoms can be very different in the quantum and classical theory 12 , indicating the possible failure of classical treatment for nuclear motion in warm dense regime. Dense hydrogen plays a crucial role in understanding the material behaviors under extreme conditions 13,14 and has important applications in energy sources 15 and astrophysics 16,17. The associated ionic and electronic transport properties are the key to tracing the dynamics of capsule implosion of inertial confinement fusion (ICF) 15 , modeling plasma processes 18 and the interior structure and evolution of giant planets and exoplanets 19-21. More exact transport properties such as thermal conductivities and electron-ion relaxation rates are required because they can remarkably alter the dynamics of planet's evolution 22 and hydrodynamical processes in ICF 23. The core pressures of some newly discovered exoplanets are estimated even up to 19 Gbar 21 , while the temperature may be several thousand Kelvins. Thanks to the recent progress in experimental techniques, one could get access to this previously inaccessible regime of phase diagram of hydrogen through a laser-induced shock wave loading of precompressed samples 24,25. However, theoretically understanding the nature of hydrogen under the ultra-high pressures is still rare and a great challenge. Density functional theory based ab initio molecular dynamics (MD) has been widely used to investigate transport properties such as ionic diffusion, electrical conductivity of dense matter at high temperatures 26-28. In viewpoint of collision physics, both the ionic and electronic transport properties depend strongly on the scattering cross sections between particles. In usual ab initio MD simulations, the corresponding scattering cross sections are statistically obtained from classical particle

Detailed-term-accounting-approximation simulation of x-ray transmission through laser-produced Al plasmas

Physical Review E, 2000

An extensive configuration interaction ͑CI͒ scheme and the R-matrix method are combined to calcul... more An extensive configuration interaction ͑CI͒ scheme and the R-matrix method are combined to calculate the x-ray transmission spectrum for high-power laser-produced Al plasmas in local thermodynamic equilibrium by using the detailed-term-accounting ͑DTA͒ approximation. All atomic parameters such as state levels and photoabsorption cross sections for different ionization stages are obtained by using the CI and R-matrix method. Special attention is given to the effects of autoionizing resonance broadening on the transmission. A large difference exists between the convergence of the results with and without taking account of autoionizing resonance broadening when the autoionization resonance broadening is the major broadening mechanism. This shows that autoionizing resonance widths of the K-shell excited states have large effects and should be considered to interpret the spectral-resolved transmission.

Radiative opacities and configuration interaction effects of hot iron plasma using a detailed term accounting model

Physical Review E, 2003

We have calculated the radiative opacities of iron plasma in local thermodynamic equilibrium usin... more We have calculated the radiative opacities of iron plasma in local thermodynamic equilibrium using a detailed term accounting model. The extensive atomic data are obtained by multiconfiguration Hartree-Fock ͑MCHF͒ method, with Breit-Pauli relativistic corrections. Extensive configuration interaction ͑CI͒ has been included based on LS coupling to obtain energy levels and the bound-bound transition cross sections. A detailed configuration accounting model is applied to evaluate the bound-free absorption cross sections. We simulate two experimental transmission spectra ͓G.

Detailed-term-accounting approximation calculations of the radiative opacity of aluminum plasmas: A systematic study

Physical Review E, 2002

The spectrally resolved radiative opacity and the Rosseland and Planck mean opacities are calcula... more The spectrally resolved radiative opacity and the Rosseland and Planck mean opacities are calculated by using the detailed-term-accounting approximation for aluminum plasmas with varieties of density and temperature. The results are presented along a 40 eV isothermal sequence, a 0.01 g/cm 3 isodense sequence, and a sequence with average ionization degree Z*ϳ7.13. Particular attention is given to the influence of the detailed treatment of spectral lines on the Rosseland mean opacity under different thermodynamical conditions. The results show that at densities of 0.004 g/cm 3 and higher, the opacities are not very sensitive to the spectral linewidth within a reasonable range. As examples, the Rosseland mean opacity, which is most sensitive to the detailed linewidth, at 40 eV and 0.004 g/cm 3 changes no more than 15%, when we change the electron impact spectral linewidth artificially by reducing it by 50% or increasing it twice, and at 40 eV and 0.1 g/cm 3 it changes less than 5%. For comparison, we also carried out calculations by using an average atom model. For the Rosseland mean opacities, the two models show quite large differences, in particular at low densities, while for the Planck mean opacities the results of the two models are much closer.

Spectrally resolved opacities and Rosseland and Planck mean opacities of lowly ionized gold plasmas: A detailed level-accounting investigation

Physical Review E, 2007

Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fu... more Calculation details of radiative opacity for lowly ionized gold plasmas by using our developed fully relativistic detailed level-accounting approach are presented to show the importance of accurate atomic data for a quantitative reproduction of the experimental observations. Even though a huge number of transition lines are involved in the radiative absorption of high-Z plasmas so that one believes that statistical models can often give a reasonable description of their opacities, we first show in detail that an adequate treatment of physical effects, in particular the configuration interaction ͑including the core-valence electron correlation͒, is essential to produce atomic data of bound-bound and bound-free processes for gold plasmas, which are accurate enough to correctly explain the relative intensity of two strong absorption peaks experimentally observed located near photon energy of 70 and 80 eV. A detailed study is also carried out for gold plasmas of an average ionization degree sequence of 10, for both spectrally resolved opacities and Rosseland and Planck means. For comparison, results obtained by using an average atom model are also given to show that even for a relatively higher density of matter, correlation effects are also important to predict the correct positions of absorption peaks of transition arrays.

Radiative opacity of gold plasmas studied by a detailed level-accounting method

Physical Review E, 2006

There are systematic discrepancies unexplained so far between theory and experiment for opacities... more There are systematic discrepancies unexplained so far between theory and experiment for opacities of midand high-Z plasmas. To address this issue, we investigated the radiative opacity of gold plasmas by using a detailed level-accounting ͑DLA͒ method, in which various physical effects can be taken into account. In this work, we studied in detail the effects of core-valence electron correlation and linewidth on the opacity of gold plasmas. Our DLA results correctly explain the relative intensity of the two strong absorption peaks located near the photon energies of 70 and 80 eV, which was experimentally observed by Eidmann et al. ͓Europhys. Lett. 44, 459 ͑1998͔͒. Meanwhile, the DLA results showed that effects of saturation for the strong individual lines are evident in the transmission spectrum.

Detailed investigations on radiative opacity and emissivity of tin plasmas in the extreme-ultraviolet region

Physical Review E, 2010

Radiative opacity and emissivity of tin plasmas at average ionization degree of about 10 was inve... more Radiative opacity and emissivity of tin plasmas at average ionization degree of about 10 was investigated in detail by using a fully relativistic detailed level accounting approach, in which main physical effects on the opacity were carefully taken into account. Among these physical effects, configuration interaction, in particular core-valence electron correlations, plays an important role on the determination of accurate atomic data required in the calculation of opacity. It results in a strong narrowing of lines from all transition arrays and strong absorption is located in a narrow wavelength region of 12.5-14 nm for Sn plasmas. Using a complete accurate atomic data, we investigated the opacity of Sn plasmas at a variety of physical condition. Among the respective ions of Xe 6+-Xe 15+ , Xe 10+ has the largest absorption cross section at 13.5 nm, while the favorable physical condition for maximal absorption at 13.5 nm do not mean that Xe 10+ has the largest fraction. Comparison with other theoretical results showed that a complete set of consistent accurate atomic data, which lacks very much, is essential to predict accurate opacity. Our atomic model is useful and can be applied to interpret opacity experiments. Further benchmark experiments are urgently needed to clarify the physical effects on the opacity of Sn plasmas.

Photoionization for the ground state of Al VII from threshold to the K shell

Physical Review A, 2001

The photoionization cross sections of N-like Al VII are calculated from the first ionization thre... more The photoionization cross sections of N-like Al VII are calculated from the first ionization threshold to 140 Ry using the R-matrix method. 14 target states ͑including 4 K-shell excited states͒ of Al VIII are included in the close-coupling calculation. The detailed structure and resonances of the cross sections across the L-shell and K-shell thresholds is described. The resonance energies and widths of some of the autoionization states are determined by analyzing the resonance structures. The results show that the autoionization width of the K-shell excited state of a 1s electron being excited into 2p orbital is the largest among all of the autoionization states. It is also larger than Doppler and Stark widths under a typical plasma condition. This result shows that the autoionization widths will have essential influence in simulating the x-ray transmission spectrum of Al plasma.

Photodetachments of the metastablensnp24Pstates ofBe−,Mg−,andCa−ions

Physical Review A, 2000

Close-coupling calculations are performed on the photodetachments of the metastable nsnp 2 4 P st... more Close-coupling calculations are performed on the photodetachments of the metastable nsnp 2 4 P states of the negative beryllium (nϭ2), magnesium (nϭ3), and calcium (nϭ4) ions by using the R-matrix method. The calculations are carried out with the consideration of excitations of one electron from core. The results show that this effect is much more important for Ca Ϫ than for Be Ϫ and Mg Ϫ. For Be Ϫ , the total and partial cross sections are obtained from the threshold to a photon energy of 0.5 Ry. The calculated total cross section exhibits two 4 P o Feshbach resonances and one 4 D o shape resonance. Close agreement is found with the available theoretical calculations and the only experimental datum of Pegg and co-workers ͓Phys. Rev. A 50, 3861 ͑1994͔͒. For the Ca Ϫ and Mg Ϫ ions, the total and partial cross sections are calculated from the threshold to a photon energy of 0.25 Ry. For the Ca Ϫ ion, the resonances are found for both 4 P o and 4 D o symmetries just below the 3 D threshold. For the M g Ϫ ion, only a 4 P o resonance is predicted. No rapid increase associated with the opening of the 4s5s 3 S channel is found in the total cross section of Ca Ϫ. The rapid increase of the photodetachment cross section of Ca Ϫ in the experiment by Hanstorp et al. ͓D. Hanstorp et al., Phys. Rev. Lett. 63, 368 ͑1989͔͒ should not be attributed to the Ca Ϫ (4s4p 2 4 P)ϩh→Ca(4s5s 3 S)ϩkp ionization process. This result is consistent with the conclusion of Petrunin and co-workers ͓Phys. Rev. Lett. 76, 744 ͑1996͔͒ that there was no Ca Ϫ (4s4p 2 4 P) ions observed by Hanstorp et al.

Level-to-level and total probability for Auger decay including direct double processes of Ar2p−1hole states

Physical Review A, 2013

Auger decay including direct double processes of Ar 2p −1 hole levels is investigated in the fram... more Auger decay including direct double processes of Ar 2p −1 hole levels is investigated in the framework of perturbation theory implemented by distorted wave approximation with balanced large-scale configuration interaction among the successive ions being taken into account. The complex transition amplitude obtained from the second perturbation theory for the direct double Auger decay (DAD) is decomposed into approximate formulas according to two generally agreed mechanisms of shake-off and knockout. Practical computations showed that the knockout condition is fulfilled and thus justified such a decomposition treatment of knockout mechanism. The contribution to the DAD probability from knockout mechanism is larger than shake-off by an order of magnitude and therefore the former is dominant. The interference effect between the knockout and shake-off mechanisms should be trivial and neglecting it we obtained a branching ratio of 12.0% for the direct DAD into triply charged states of Ar 3+. By including cascade double decay, a total branching ratio of 14.9% is obtained. Our result explained recent experimental results on the branching ratio into triply charged ion, and should be useful for further detailed experimental investigations.

Inner-shell resonant absorption effects on evolution dynamics of the charge state distribution in a neon atom interacting with ultraintense x-ray pulses

Physical Review A, 2012

Inner-shell resonant absorption (IRA) effects were investigated on evolution dynamics of charge s... more Inner-shell resonant absorption (IRA) effects were investigated on evolution dynamics of charge state distribution (CSD) in the interaction of ultraintense x-ray pulses with a neon atom. IRA is the physical origin of the large discrepancies found between theory and experiment at a photon energy of 1050 eV [L. Young et al., Nature (London) 466, 56 (2010)], where the rates of K-shell resonant absorption 1s → 4p of Ne 6+ and 1s → 3p of Ne 7+ are larger than the direct single-photon ionization rates by more than one order of magnitude, and hence IRA becomes the dominant absorption mechanism. Only when the IRA effects are properly taken into account can we correctly explain the observed CSD.