Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon ...Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon dioxide upon electron-impact.Through fragment ions and electron coincidence momentum imaging,we unambiguously determine the ionization mechanism by measuring the projectile energy loss in association with the C^(+) +O_(2)^(+) channel.Further potential energy and trajectory calculations enable us to elucidate the dynamical details of this fragmentation process,in which a bond rearrangement pathway is found to proceed via the structural deformation to a triangular intermediate.Moreover,we demonstrate a further roaming pathway for the formation of O_(2)^(+) from CO_(2)^(+) 2,in which a frustrated C-O bond cleavage leaves the O atom without sufficient energy to escape.The O atom then wanders around varied configuration spaces of the flat potential energy regions and forms a C-O-O_(2)^(+) intermediate prior to the final products C^(+) +O_(2)^(+).Considering the large quantities of free electrons in interstellar space,the processes revealed here are expected to be significant and should be incorporated into atmospheric evolution models.展开更多
Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,...Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,but it is typically unattainable in a circularly polarized laser pulse,especially for long-wavelength lasers.We present evidence that NSDI can occur in the presence of a near-infrared or beyond laser pulse by introducing a bowtie-nanotip.The laser-induced local plasmon can alter the local ellipticity of the feld,thereby enabling NSDI through elliptical trajectories that facilitate recollisions with parent atoms.An oval-shaped momentum distribution of recoiled ions provides evidence for the modifcation of trajectories by the aligned nanotips.Our study introduces an innovative control knob to manipulate NSDI and electron dynamics through the utilization of nanostructures.展开更多
With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our resu...With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.展开更多
We theoretically investigate the frustrated double ionization(FDI)of molecules with different alignment-dependence using a three-dimensional classical ensemble method.The numerical results show that the FDI probabilit...We theoretically investigate the frustrated double ionization(FDI)of molecules with different alignment-dependence using a three-dimensional classical ensemble method.The numerical results show that the FDI probability decreases with increasing wavelength,which is similar to the wavelength dependence of the FDI probability of atoms.Tracing the classical trajectories reveals that the contributions to molecular FDI from single-recollision and multiple-recollision mechanisms are equal in the short wavelength regime.In the long wavelength regime,the single-recollision FDI channel dominates in FDI.The nature in which molecular FDI occurs is identified and explained.展开更多
We investigate the nonsequential double ionization(NSDI) of linear triatomic molecules by the counter-rotating two-color circularly polarized(CRTC) laser fields with a classical ensemble method. The results of the sim...We investigate the nonsequential double ionization(NSDI) of linear triatomic molecules by the counter-rotating two-color circularly polarized(CRTC) laser fields with a classical ensemble method. The results of the simulation reveal that NSDI yield strongly connected with the relative phase. The trajectory tracking method shows that the return time of the electron is controlled by the relative phase. In addition, when we change the CRTC laser wavelengths, the relative phase of the maximum and minimum yield of NSDI also changes. This shows that the influence of the Coulomb potential in the triatomic molecules on the electron return process cannot be ignored. This work will effectively promote the electronic dynamics study of NSDI for the triatomic molecule.展开更多
The two-photon double ionization（TPDI） dynamics of helium by chirped attosecond pulses are theoretically studied by solving the two-electron time-dependent Schr o¨dinger equation in its full dimensions. We show...The two-photon double ionization（TPDI） dynamics of helium by chirped attosecond pulses are theoretically studied by solving the two-electron time-dependent Schr o¨dinger equation in its full dimensions. We show that both the differential and the total double ionization probability can be significantly controlled by adjusting the chirp. The dependence of the TPDI on the chirp can be quite different for different photon energies, relying on the central photon energy being in the sequential region, nonsequential region, or translation region. The physics which lead to the chirp dependence for different photon energies are addressed. Present findings are well reproduced by a model based on the second-order time-dependent perturbation theory.展开更多
Nonsequential double ionization （NSDI） processes of nonaligned diatomic molecules N2 and O2 are studied using the S-matrix theory. Our results show that the NSDI process significantly depends on the molecular symmet...Nonsequential double ionization （NSDI） processes of nonaligned diatomic molecules N2 and O2 are studied using the S-matrix theory. Our results show that the NSDI process significantly depends on the molecular symmetry and structure. The ratio of NSDI rate to single ionization rate as a function of the field intensity is obtained. It is found that N2 behaves closely with its companion atom Ar in the ratios over the entire intensity range, while O2 exhibits an obvious suppression effect, which is qualitatively consistent with the experiment.展开更多
We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrat...We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrate an unambiguous interference feature in the photoelectron spectra, and the interference is unveiled to originate from the dynamic Stark effect. The interference photoelectron spectra are prompted for intense sub-femtosecond XUV laser pulses in double ionization. The stationary phase picture is corroborated qualitatively in the two-electron system. The ability of probing the dynamic Stark effect by the photoelectron spectra in a pragmatic experiment of single-photon double ionization of He may shed light on further investigation on multi-electron atoms and molecules.展开更多
With the classical ensemble model, we investigate nonsequential double ionization （NSDI） of xenon atoms using 780 nm, 0.25 PW/cm2 elliptically polarized few-cycle laser pulses. The momentum distribution of correlate...With the classical ensemble model, we investigate nonsequential double ionization （NSDI） of xenon atoms using 780 nm, 0.25 PW/cm2 elliptically polarized few-cycle laser pulses. The momentum distribution of correlated electron along the long axis o~ the laser polarization plane shows an obvious V-like structure locating at the third quadrant, and the momentum along the short axis of the laser polarization plane are mainly distributed in the second and fourth quadrants. Moreover, we demonstrate that the Coulomb repulsion interaction plays a decisive role to the above results. By back analyzing the class/ca/ trajectories of NSDI, we find that there are two kinds of recollision trajectories mainly contribute to NSDI, and the different microscopic dynamics for the two kinds of trajectories are clearly explored.展开更多
Using a classical ensemble model, we investigate the correlation behaviour of electrons originating from nonsequential double ionization （NSDI） of argon atoms by the elliptically polarized laser pulses. Because of t...Using a classical ensemble model, we investigate the correlation behaviour of electrons originating from nonsequential double ionization （NSDI） of argon atoms by the elliptically polarized laser pulses. Because of the ellipticity, not only the first electron to return but also the later return of tunneled electrons contribute significantly to NSDI. We mainly discuss two kinds of events of NSDI originating from the first and the second return separately. For the NSDI resulting from the recollision of the first return, the correlated electron momentum spectrum along the long axis of the laser polarization plane reveals an obvious V-like shape, located at the first and third quadrant. However, for the NSDI resulting from the recollision of the second return, the momenta of two electrons are distributed in the four quadrants uniformly. By analysing the trajectories of these two kinds, we find that the recollision energy and the laser phase at recollision are different for the first and second returning trajectories, which are responsible for the difference in the correlated behavior of the final electron momentum.展开更多
Using the classical ensemble model, we investigate the nonsequential double ionization（NSDI） of Ar and Mg in the two-color elliptically polarized laser pulse for different elliptical polarizations. Numerical results...Using the classical ensemble model, we investigate the nonsequential double ionization（NSDI） of Ar and Mg in the two-color elliptically polarized laser pulse for different elliptical polarizations. Numerical results show that for Ar atoms the NSDI yield increases as the ellipticity increases, which is different from the case of Mg atoms. Moreover, the correlated behavior in the correlated electron momentum along the x direction and ion momentum distributions of Ar atoms are influenced by the ellipticity. By statistical analysis of different times, we can conclude that the ellipticity may be responsible for the NSDI processes. The correlated momenta distributions along the x direction at the recollision time are demonstrated and the results show that the travelling time and ellipticity can affect the emitted directions of both electrons.展开更多
We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and disti...We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI,which are recollision–impact ionization(RII)and recollision-induced excitation with subsequent ionization(RESI),according to the delay-time between the recollision and the final double ionization.The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase.We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.展开更多
We experimentally investigate the double ionization pulses. The total kinetic energy release of the two of molecular hydrogen subjected to ultrashort intense laser coincident H＋ ions, which provides a diagnosis of di...We experimentally investigate the double ionization pulses. The total kinetic energy release of the two of molecular hydrogen subjected to ultrashort intense laser coincident H＋ ions, which provides a diagnosis of different processes to double ionization of H2, is measured for two different pulse durations, i.e., 25 and 5 fs, and various laser intensities. It is found that, for the long pulse duration （i.e., 25 fs）, the double ionization occurs mainly via two processes, i.e., the charge resonance enhanced ionization and recollision-induced double ionization. Moreover, the contributions from these two processes can be significantly modulated by changing the laser intensity. In contrast, for a few-cycle pulse of 5 fs, only the recollsion-induced double ionization survives, and in particular, this process could be solely induced by the first-return reeollision at appropriate laser intensities, providing an efficient way to probe the sub-laser-cycle molecular dynamics.展开更多
The microscopic recollision dynamics in strong-field nonsequential double ionization of Ar atoms is in- vestigated using three-dimensional classical ensembles. By adjusting the nuclear Coulomb potential, we can excell...The microscopic recollision dynamics in strong-field nonsequential double ionization of Ar atoms is in- vestigated using three-dimensional classical ensembles. By adjusting the nuclear Coulomb potential, we can excellently reproduce the experimental results both within the laser intensity regimes well above the reeollision threshold and well below the recollision threshold quantitatively. More importantly, our trajectory analysis clearly reveals the particular electronic dynamics in recollision process： the momentum of the recolliding electron encounters a sudden change both in magnitude and in direction when it approaches the nucleus closely, which show that the nuclear Coulomb attraction plays a key role in the recollision process of nonsequential double ionization of Ar atoms.展开更多
In strong-field double ionization,two electrons are ionized by intense laser field.These two electrons move in the laser field and the state is described by a Coulomb-Volkov state,where the repulsive Coulomb state des...In strong-field double ionization,two electrons are ionized by intense laser field.These two electrons move in the laser field and the state is described by a Coulomb-Volkov state,where the repulsive Coulomb state describes the relative motion of the two electrons and the Volkov state describes the center-of-mass motion of the two electrons in the laser field.In the frame of scattering theory,we derive a simple analytical formula of the double ionization of He-like atoms.The effect of the Coulomb force between two electrons on the double ionization process is discussed.Numerical studies disclose that the Coulomb force enhances the ionization rate of high-energy electrons but suppresses the ionization rate of the lowest-energy electrons.展开更多
The double ionization process of molecules driven by co-rotating two-color circularly polarized fields is investigated with a three-dimensional classical ensemble model. Numerical results indicate that a considerable ...The double ionization process of molecules driven by co-rotating two-color circularly polarized fields is investigated with a three-dimensional classical ensemble model. Numerical results indicate that a considerable part of the sequential double ionization(DI) events of molecules occur through internal collision double ionization(ICD), and the ICD recollision mechanism is significantly different from that in non-sequential double ionization(NSDI). By analyzing the results of internuclear distances R = 5 a.u. and 2 a.u., these two recollision mechanisms are studied in depth. It is found that the dynamic behaviors of the recollision mechanisms of NSDI and ICD are similar. For NSDI, the motion range of electrons after the ionization is relatively large, and the electrons will return to the core after a period of time. In the ICD process,electrons will rotate around the parent ion before ionization, and the distance of the electron motion is relatively small. After a period of time, the electrons will come back to the core and collide with another electron. Furthermore, the molecular internuclear distance has a significant effect on the electron dynamic behavior of the two ionization mechanisms. This study will help to understand the multi-electron ionization process of complex systems.展开更多
We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V ...We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.展开更多
Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)la...Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)laser field is theoretically studied.And the dynamics in two typical collision pathways,recollision-impact-ionization(RII)and recollisionexcitation with subsequent ionization(RESI),is systematically explored.Our results reveal that the V-shaped structure in the correlated momentum distribution is mainly caused by the RII mechanism when the relative amplitude of the OTC laser field is zero,and the first ionized electrons will quickly skim through the nucleus and share few energy with the second electron.As the relative amplitude increases,the V-shaped structure gradually disappears and electrons are concentrated on the diagonal in the electron correlation spectrum,indicating that the energy sharing after electrons collision is symmetric for OTC laser fields with large relative amplitudes.Our studies show that changing the relative amplitude of the OTC laser field can efficiently control the electron–electron collisions and energy exchange efficiency in the NSDI process.展开更多
Recently,the quantitative rescattering model(QRS)for nonsequential double ionization(NSDI)is modified by taking into account the potential change(PC)due to the presence of electric field at the time of recollision.Usi...Recently,the quantitative rescattering model(QRS)for nonsequential double ionization(NSDI)is modified by taking into account the potential change(PC)due to the presence of electric field at the time of recollision.Using the improved QRS model,we simulate the longitudinal momentum distributions of doubly charged ions He2+by projecting the correlated two-electron momentum distributions for NSDI of He onto the main diagonal.The obtained results are compared directly with the experimental data at different intensities.It is found that when the PC is considered,the width of momentum distributions reduces and the agreement between theory and experiment is improved.展开更多
The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that...The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos.12325406,92261201,12404305,and W2512072)the Shaanxi Province Natural Science Fundamental Research Project (Grant Nos.2023JC-XJ-03 and23JSQ013)the China Postdoctoral Science Foundation (Grant Nos.BX20240286 and 2024M7625)。
文摘Abiotic oxygen formation predates photosynthesis,sustaining early chemical evolution,yet its elementary mechanisms remain contested.Here,we show the production pathways for molecular oxygen from doubly ionized carbon dioxide upon electron-impact.Through fragment ions and electron coincidence momentum imaging,we unambiguously determine the ionization mechanism by measuring the projectile energy loss in association with the C^(+) +O_(2)^(+) channel.Further potential energy and trajectory calculations enable us to elucidate the dynamical details of this fragmentation process,in which a bond rearrangement pathway is found to proceed via the structural deformation to a triangular intermediate.Moreover,we demonstrate a further roaming pathway for the formation of O_(2)^(+) from CO_(2)^(+) 2,in which a frustrated C-O bond cleavage leaves the O atom without sufficient energy to escape.The O atom then wanders around varied configuration spaces of the flat potential energy regions and forms a C-O-O_(2)^(+) intermediate prior to the final products C^(+) +O_(2)^(+).Considering the large quantities of free electrons in interstellar space,the processes revealed here are expected to be significant and should be incorporated into atmospheric evolution models.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFE0134200)the National Natural Science Foundation of China(Grant Nos.12474343,12174147,and 12074142)the Natural Science Foundation of Jilin Province,China(Grant No.20220101016JC)。
文摘Strong feld-induced nonsequential double ionization(NSDI)is a signifcant multi-electron phenomenon that provides crucial insights into understanding electron correlation and multiple ionization of atoms and molecules,but it is typically unattainable in a circularly polarized laser pulse,especially for long-wavelength lasers.We present evidence that NSDI can occur in the presence of a near-infrared or beyond laser pulse by introducing a bowtie-nanotip.The laser-induced local plasmon can alter the local ellipticity of the feld,thereby enabling NSDI through elliptical trajectories that facilitate recollisions with parent atoms.An oval-shaped momentum distribution of recoiled ions provides evidence for the modifcation of trajectories by the aligned nanotips.Our study introduces an innovative control knob to manipulate NSDI and electron dynamics through the utilization of nanostructures.
基金supported by the National Natural Science Foundation of China (Grant No. 12074329)Nanhu Scholars Program for Young Scholars of Xinyang Normal University。
文摘With a three-dimensional semiclassical ensemble method, we theoretically investigated the nonsequential double ionization of Ar driven by the spatially inhomogeneous few-cycle negatively chirped laser pulses. Our results show that the recollision time window can be precisely controlled within an isolated time interval of several hundred attoseconds, which is useful for understanding the subcycle correlated electron dynamics. More interestingly, the correlated electron momentum distribution (CEMD) exhibits a strong dependence on laser intensity. That is, at lower laser intensity, CEMD is located in the first quadrant. As the laser intensity increases,CEMD shifts almost completely to the second and fourth quadrants, and then gradually to the third quadrant.The underlying physics governing the CEMD's dependence on laser intensity is explained.
基金Supported by the National Natural Science Foundation of China(Grant Nos.12004323,12074329,12104389,1174131 and 91850114)National Key R&D Program of China(2022YFE0134200)+2 种基金Nanhu Scholars Program for Young Scholars of Xinyang Normal UniversityNatural Science Foundation of Jilin Province,China(Grant No.20220101016JC)the Open Research Fund of State Key Laboratory of Transient Optics and Photonics。
文摘We theoretically investigate the frustrated double ionization(FDI)of molecules with different alignment-dependence using a three-dimensional classical ensemble method.The numerical results show that the FDI probability decreases with increasing wavelength,which is similar to the wavelength dependence of the FDI probability of atoms.Tracing the classical trajectories reveals that the contributions to molecular FDI from single-recollision and multiple-recollision mechanisms are equal in the short wavelength regime.In the long wavelength regime,the single-recollision FDI channel dominates in FDI.The nature in which molecular FDI occurs is identified and explained.
基金supported by the Natural Science Foundation of Shanghai (Grant No. 18ZR1413600)。
文摘We investigate the nonsequential double ionization(NSDI) of linear triatomic molecules by the counter-rotating two-color circularly polarized(CRTC) laser fields with a classical ensemble method. The results of the simulation reveal that NSDI yield strongly connected with the relative phase. The trajectory tracking method shows that the return time of the electron is controlled by the relative phase. In addition, when we change the CRTC laser wavelengths, the relative phase of the maximum and minimum yield of NSDI also changes. This shows that the influence of the Coulomb potential in the triatomic molecules on the electron return process cannot be ignored. This work will effectively promote the electronic dynamics study of NSDI for the triatomic molecule.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11322437 and 11574010)the National Basic Research Project of China(Grant No.2013CB922402)
文摘The two-photon double ionization（TPDI） dynamics of helium by chirped attosecond pulses are theoretically studied by solving the two-electron time-dependent Schr o¨dinger equation in its full dimensions. We show that both the differential and the total double ionization probability can be significantly controlled by adjusting the chirp. The dependence of the TPDI on the chirp can be quite different for different photon energies, relying on the central photon energy being in the sequential region, nonsequential region, or translation region. The physics which lead to the chirp dependence for different photon energies are addressed. Present findings are well reproduced by a model based on the second-order time-dependent perturbation theory.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074026, 11074155, and 11104225)the Program for New Century Excellent Talents in University of the Ministry of Education of China (Grant No. NCET-08-0883)the National Basic Research Program of China (Grant No. 2011CB808100)
文摘Nonsequential double ionization （NSDI） processes of nonaligned diatomic molecules N2 and O2 are studied using the S-matrix theory. Our results show that the NSDI process significantly depends on the molecular symmetry and structure. The ratio of NSDI rate to single ionization rate as a function of the field intensity is obtained. It is found that N2 behaves closely with its companion atom Ar in the ratios over the entire intensity range, while O2 exhibits an obvious suppression effect, which is qualitatively consistent with the experiment.
基金Supported by the National Natural Science Foundation of China under Grant Nos 61178028,11674243 and 11674242the National Basic Research Program of China under Grant No 2015CB755403
文摘We report our numerical simulation on the dynamic interference photoelectron spectra for a one-dimensional （1D） He model exposed to intense ultrashort extreme ultraviolet （XUV） laser pulses. The results demonstrate an unambiguous interference feature in the photoelectron spectra, and the interference is unveiled to originate from the dynamic Stark effect. The interference photoelectron spectra are prompted for intense sub-femtosecond XUV laser pulses in double ionization. The stationary phase picture is corroborated qualitatively in the two-electron system. The ability of probing the dynamic Stark effect by the photoelectron spectra in a pragmatic experiment of single-photon double ionization of He may shed light on further investigation on multi-electron atoms and molecules.
基金Supported by the National Natural Science Foundation of China under Grant Nos.11005088and11047145the Basic and Advanced Technology of Henan Province of China under Grant Nos.102300410241and112300410021the Scientific Research Foundation of Education Department of Henan Province of China under Grant Nos.2011B140018and13A140774
文摘With the classical ensemble model, we investigate nonsequential double ionization （NSDI） of xenon atoms using 780 nm, 0.25 PW/cm2 elliptically polarized few-cycle laser pulses. The momentum distribution of correlated electron along the long axis o~ the laser polarization plane shows an obvious V-like structure locating at the third quadrant, and the momentum along the short axis of the laser polarization plane are mainly distributed in the second and fourth quadrants. Moreover, we demonstrate that the Coulomb repulsion interaction plays a decisive role to the above results. By back analyzing the class/ca/ trajectories of NSDI, we find that there are two kinds of recollision trajectories mainly contribute to NSDI, and the different microscopic dynamics for the two kinds of trajectories are clearly explored.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11005088 and 11047145)the Project of Basic and Advanced Technology of Henan Province, China (Grant Nos. 102300410241 and 112300410021)the Scientific Research Foundation of Education Department of Henan Province,China (Grant No. 2011B140018)
文摘Using a classical ensemble model, we investigate the correlation behaviour of electrons originating from nonsequential double ionization （NSDI） of argon atoms by the elliptically polarized laser pulses. Because of the ellipticity, not only the first electron to return but also the later return of tunneled electrons contribute significantly to NSDI. We mainly discuss two kinds of events of NSDI originating from the first and the second return separately. For the NSDI resulting from the recollision of the first return, the correlated electron momentum spectrum along the long axis of the laser polarization plane reveals an obvious V-like shape, located at the first and third quadrant. However, for the NSDI resulting from the recollision of the second return, the momenta of two electrons are distributed in the four quadrants uniformly. By analysing the trajectories of these two kinds, we find that the recollision energy and the laser phase at recollision are different for the first and second returning trajectories, which are responsible for the difference in the correlated behavior of the final electron momentum.
基金Project supported by the National Natural Science Foundation of China(Grant No.61575077)the Natural Science Foundation of Jilin Province,China(Grant No.20180101225JC)
文摘Using the classical ensemble model, we investigate the nonsequential double ionization（NSDI） of Ar and Mg in the two-color elliptically polarized laser pulse for different elliptical polarizations. Numerical results show that for Ar atoms the NSDI yield increases as the ellipticity increases, which is different from the case of Mg atoms. Moreover, the correlated behavior in the correlated electron momentum along the x direction and ion momentum distributions of Ar atoms are influenced by the ellipticity. By statistical analysis of different times, we can conclude that the ellipticity may be responsible for the NSDI processes. The correlated momenta distributions along the x direction at the recollision time are demonstrated and the results show that the travelling time and ellipticity can affect the emitted directions of both electrons.
基金Project supported by the National Natural Science Foundation of China(Grant No.61575077)the Natural Science Foundation of Jilin Province of China(Grant No.20180101225JC)
文摘We investigated the nonsequential double ionization(NSDI)in Ar by two-color elliptically polarized laser field with a three-dimensional(3D)classical ensemble method.We study the relative phase effect of NSDI and distinguish two particular recollision channels in NSDI,which are recollision–impact ionization(RII)and recollision-induced excitation with subsequent ionization(RESI),according to the delay-time between the recollision and the final double ionization.The numerical results indicate that the ion momentum distribution is changed and the triangle structure is more obvious with the decrease of the relative phase.We also demonstrate that the RESI process always dominates in the whole double ionization process and the ratio of RESI and RII channels can be influenced by the relative phase.
基金Supported by the National Basic Research Program of China under Grant No 2013CB922201the National Natural Science Foundation of China under Grant Nos 11304365,11374329 and 11334009
文摘We experimentally investigate the double ionization pulses. The total kinetic energy release of the two of molecular hydrogen subjected to ultrashort intense laser coincident H＋ ions, which provides a diagnosis of different processes to double ionization of H2, is measured for two different pulse durations, i.e., 25 and 5 fs, and various laser intensities. It is found that, for the long pulse duration （i.e., 25 fs）, the double ionization occurs mainly via two processes, i.e., the charge resonance enhanced ionization and recollision-induced double ionization. Moreover, the contributions from these two processes can be significantly modulated by changing the laser intensity. In contrast, for a few-cycle pulse of 5 fs, only the recollsion-induced double ionization survives, and in particular, this process could be solely induced by the first-return reeollision at appropriate laser intensities, providing an efficient way to probe the sub-laser-cycle molecular dynamics.
基金Supported by the National Natural Science Foundation of China under Grant Nos. 11005088 and 11047145the Science & Technology Project of Henan Province in China under Grant Nos. 102300410241 and 112300410021the Scientific Research Foundation of Education Department of Henan Province in China under Grant Nos. 2009A140006 and 2011B140018
文摘The microscopic recollision dynamics in strong-field nonsequential double ionization of Ar atoms is in- vestigated using three-dimensional classical ensembles. By adjusting the nuclear Coulomb potential, we can excellently reproduce the experimental results both within the laser intensity regimes well above the reeollision threshold and well below the recollision threshold quantitatively. More importantly, our trajectory analysis clearly reveals the particular electronic dynamics in recollision process： the momentum of the recolliding electron encounters a sudden change both in magnitude and in direction when it approaches the nucleus closely, which show that the nuclear Coulomb attraction plays a key role in the recollision process of nonsequential double ionization of Ar atoms.
基金the National Natural Science Foundation of China(Grant Nos.11674231 and 12074261)the Shanghai Natural Science Foundation,China(Grant No.20ZR1441600).
文摘In strong-field double ionization,two electrons are ionized by intense laser field.These two electrons move in the laser field and the state is described by a Coulomb-Volkov state,where the repulsive Coulomb state describes the relative motion of the two electrons and the Volkov state describes the center-of-mass motion of the two electrons in the laser field.In the frame of scattering theory,we derive a simple analytical formula of the double ionization of He-like atoms.The effect of the Coulomb force between two electrons on the double ionization process is discussed.Numerical studies disclose that the Coulomb force enhances the ionization rate of high-energy electrons but suppresses the ionization rate of the lowest-energy electrons.
基金the National Key Research and Development Program of China (Grant No.2019YFA0307700)the National Natural Science Foundation of China (Grant Nos.12074145 and 11975012)+1 种基金Jilin Provincial Research Foundation for Basic Research,China (Grant No.20220101003JC)Jilin Provincial Education Department (Grant No.JJKH20230284KJ)。
文摘The double ionization process of molecules driven by co-rotating two-color circularly polarized fields is investigated with a three-dimensional classical ensemble model. Numerical results indicate that a considerable part of the sequential double ionization(DI) events of molecules occur through internal collision double ionization(ICD), and the ICD recollision mechanism is significantly different from that in non-sequential double ionization(NSDI). By analyzing the results of internuclear distances R = 5 a.u. and 2 a.u., these two recollision mechanisms are studied in depth. It is found that the dynamic behaviors of the recollision mechanisms of NSDI and ICD are similar. For NSDI, the motion range of electrons after the ionization is relatively large, and the electrons will return to the core after a period of time. In the ICD process,electrons will rotate around the parent ion before ionization, and the distance of the electron motion is relatively small. After a period of time, the electrons will come back to the core and collide with another electron. Furthermore, the molecular internuclear distance has a significant effect on the electron dynamic behavior of the two ionization mechanisms. This study will help to understand the multi-electron ionization process of complex systems.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 12174034, 12047510, and 11822401)NSAF (Grant Nos. U1930402 and U1930403)。
文摘We study the double ionization dynamics of a helium atom impacted by electrons with full-dimensional classical trajectory Monte Carlo simulation. The excess energy is chosen to cover a wide range of values from 5 e V to 1 ke V for comparative study. At the lowest excess energy, i.e., close to the double-ionization threshold, it is found that the projectile momentum is totally transferred to the recoil-ion while the residual energy is randomly partitioned among the three outgoing electrons, which are then most probably emitted with an equilateral triangle configuration. Our results agree well with experiments as compared with early quantum-mechanical calculation as well as classical simulation based on a two-dimensional Bohr's model. Furthermore, by mapping the final momentum vectors event by event into a Dalitz plot,we unambiguously demonstrate that the ergodicity has been reached and thus confirm a long-term scenario conceived by Wannier. The time scale for such few-body thermalization, from the initial nonequilibrium state to the final microcanonical distribution, is only about 100 attoseconds. Finally, we predict that, with the increase of the excess energy, the dominant emission configuration undergoes a transition from equilateral triangle to T-shape and finally to a co-linear mode. The associated signatures of such configuration transition in the electron–ion joint momentum spectrum and triple-electron angular distribution are also demonstrated.
基金Project supported by the National Natural Science Foundation of China (Grant Nos.12204132 and 12304376)Excellent Youth Science Foundation of Shandong Province (Overseas) (Grant No.2022HWYQ-073)+1 种基金the Fundamental Research Funds for the Central Universities (Grant No.HIT.OCEF.2022042)Natural Science Foundation of Shandong Province (Grant No.ZR2023QA075)。
文摘Using the semiclassical ensemble model,the dependence of relative amplitude for the recollision dynamics in nonsequential double ionization(NSDI)of neon atom driven by the orthogonally polarized two-color field(OTC)laser field is theoretically studied.And the dynamics in two typical collision pathways,recollision-impact-ionization(RII)and recollisionexcitation with subsequent ionization(RESI),is systematically explored.Our results reveal that the V-shaped structure in the correlated momentum distribution is mainly caused by the RII mechanism when the relative amplitude of the OTC laser field is zero,and the first ionized electrons will quickly skim through the nucleus and share few energy with the second electron.As the relative amplitude increases,the V-shaped structure gradually disappears and electrons are concentrated on the diagonal in the electron correlation spectrum,indicating that the energy sharing after electrons collision is symmetric for OTC laser fields with large relative amplitudes.Our studies show that changing the relative amplitude of the OTC laser field can efficiently control the electron–electron collisions and energy exchange efficiency in the NSDI process.
基金Project supported by the National Natural Science Foundation of China(Grant No.11274219)the Science and Technology Planning Project of Guangdong Province of China(Grant No.180917124960522)the Program for Promotion of Science at Universities in Guangdong Province of China(Grant No.2018KTSCX062)。
文摘Recently,the quantitative rescattering model(QRS)for nonsequential double ionization(NSDI)is modified by taking into account the potential change(PC)due to the presence of electric field at the time of recollision.Using the improved QRS model,we simulate the longitudinal momentum distributions of doubly charged ions He2+by projecting the correlated two-electron momentum distributions for NSDI of He onto the main diagonal.The obtained results are compared directly with the experimental data at different intensities.It is found that when the PC is considered,the width of momentum distributions reduces and the agreement between theory and experiment is improved.
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 11074026 and 11074155)the Program for New Century Excellent Talents in University of the Ministry of Education of China (Grant No. NCET-08-0883)
文摘The effect of initial longitudinal velocity of the tunnelled electron on the non-sequential double ionization （NSDI） process in an elliptically polarized laser field is studied by a semiclassical model. We find that the non-zero initial longitudinal velocity has a suppressing effect on single-return collision （SRC） events in the double ionization process, more specifically, it results in an obvious reduction in the center part of the correlation momentum distributions in the direction of the major polarization axis （z axis） and makes the distribution of single-return collision in the minor polarization axis （x axis） become narrower.
