By numerically solving the time-dependent Schr¨odinger equation, we observe a remarkable strong-field interference pattern in the photoelectron momentum distribution of a hydrogen atom ionized by a few-cycles las...By numerically solving the time-dependent Schr¨odinger equation, we observe a remarkable strong-field interference pattern in the photoelectron momentum distribution of a hydrogen atom ionized by a few-cycles laser pulse. This interference pattern is joined together with the familiar near-forward strong-field photoelectron holographic interference. By applying the strong-field approximation theory, we investigate the formation of this interference pattern, which arises from the interference between the backward rescattered part and the direct part of the tunneling ionized electron wave packet. We demonstrate that this backward rescattered photoelectron holographic interference can also be observed in a more realistic parallel two-color laser field. These results pave a new way to look into the atomic and molecular structure with ultrafast timescale.展开更多
Coherent superposition of electronic states induces attosecond electron motion in molecules.We theoretically investigate the strong-field ionization of this superposition state by numerically solving the time-dependen...Coherent superposition of electronic states induces attosecond electron motion in molecules.We theoretically investigate the strong-field ionization of this superposition state by numerically solving the time-dependent Schrodinger equation.In the obtained photoelectron momentum distribution,an intriguing bifurcation structure appears in the strong-field holographic interference pattern.We demonstrate that this bifurcation structure directly provides complete information about the status of the transient wave function of the superposition state:the horizontal location of the bifurcation in the momentum distribution reveals the relative phase of the involved components of the superposition state and the vertical position indicates the relative coefficient.Thus,this bifurcation structure takes a snapshot of the transient electron wave packet of the superposition state and provides an intuitive way to monitor electron motion in molecules.展开更多
We develop a numerical scheme for solving the one-dimensional(1D)time-dependent Schrödinger equation(TDSE),and use it to study the strong-field photoionization of the atomic hydrogen.The photoelectron energy spec...We develop a numerical scheme for solving the one-dimensional(1D)time-dependent Schrödinger equation(TDSE),and use it to study the strong-field photoionization of the atomic hydrogen.The photoelectron energy spectra obtained for pulses ranging from XUV to near infrared are compared in detail to the spectra calculated with our well-developed code for accurately solving the three-dimensional(3D)TDSE.For XUV pulses,our discussions cover intensities at which the ionization is in the perturbative and nonperturbative regimes.For pulses of 400 nm or longer wavelengths,we distinguish the multiphoton and tunneling regimes.Similarities and discrepancies between the 1D and 3D calculations in each regime are discussed.The observed discrepancies mainly originate from the differences in the transition matrix elements and the energy level structures created in the 1D and 3D calculations.展开更多
Photoelectron momentum distribution of hydrogen molecular ion in a circularly polarized laser pulse is calculated by solving the three-dimensional time-dependent Schrodinger equation(3D-TDSE).At the intermediate inter...Photoelectron momentum distribution of hydrogen molecular ion in a circularly polarized laser pulse is calculated by solving the three-dimensional time-dependent Schrodinger equation(3D-TDSE).At the intermediate internuclear distance,an unusual multi-peak structure is observed in the angular distribution,which is proved to be a signature of the transient localization of the electron upon alternating nucleus.By tracing the time-dependent ionization rate and bound state populations,we provide a clear evidence that the transient electron localization still exists in circularly polarized pulse and the corresponding multiple ionization bursts are directly mapped onto observable angular distributions.In addition,we introduce an intuitive strong-field approximation model which incorporates laser-induced subcycle internal electron dynamics to isolate the effect of the Coulomb potential of the parent ions.In this way,the timing of each ionization burst can be directly read out from the angular distributions.Our results suggest that the ionization time serves as a sensitive tool encoding intramolecular electron dynamics and can be measured using attoclock technique.展开更多
Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits.Identifying the contributions of these orbits is crucial for exploring the application ...Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits.Identifying the contributions of these orbits is crucial for exploring the application of tunneling and for understanding various tunneling-triggered strong-field phenomena.We perform a combined experimental and theoretical study to identify the relative contributions of the quantum orbits corresponding to the electrons tunneling ionized during the adjacent rising and falling quarter cycles of the electric field of the laser pulse.In our scheme,a perturbative second-harmonic field is added to the fundamental driving field.By analyzing the relative phase dependence of the signal in the photoelectron momentum distribution,the relative contributions of these two orbits are unambiguously determined.Our results show that their relative contributions sensitively depend on the longitudinal momentum and modulate with the transverse momentum of the photoelectron,which is attributed to the interference of the electron wave packets of the long orbit.The relative contributions of these orbits resolved here are important for the application of strong-field tunneling ionization as a photoelectron spectroscopy for attosecond time-resolved measurements.展开更多
Strong-field tunneling ionization is the first step for a broad class of phenomena in intense laser-atom/molecule interactions. Accurate information about the electron wave packet from strong-field tunneling ionizatio...Strong-field tunneling ionization is the first step for a broad class of phenomena in intense laser-atom/molecule interactions. Accurate information about the electron wave packet from strong-field tunneling ionization of atoms and molecules is of essential importance for understanding various tunneling ionization triggered processes. Here, we survey the property of the electron wave packet in tunneling ionization of molecules with a method based on strong-field photoelectron holography. By solving the time-dependent Schr ¨odinger equation, it is shown that the holographic interference in the photoelectron momentum distribution exhibits the asymmetric behavior with respect to the laser polarization direction, when the molecule is aligned with a nonzero angle to the linearly polarized laser field. We demonstrate that this asymmetry is due to the nonzero initial transverse displacement of the electron wave packet at tunneling. By analyzing the holographic interference, this transverse displacement for the launching of electron wave packet tunneling from the molecules is accurately retrieved. This displacement is directly related to the electron density distribution in molecules, and thus our work developed a novel concept for probing electronic structure in molecules.展开更多
The spiderlike structures in the photoelectron momentum distributions of ionized electrons from the hydrogen atom are numerically simulated by using a semiclassical rescattering model(SRM) and solving the time-depende...The spiderlike structures in the photoelectron momentum distributions of ionized electrons from the hydrogen atom are numerically simulated by using a semiclassical rescattering model(SRM) and solving the time-dependent Schrodinger equation(TDSE),focusing on the role of the phase of the scattering amplitude.With the SRM,we find that the spiderlike legs shift to positions with smaller transverse momentum values while increasing the phase.The spiderlike patterns obtained by SRM and TDSE are in good agreement upon considering this phase.In addition,the time differences in electron ionization and rescattering calculated by SRM and the saddle-point equations are either in agreement or show very similar laws of variation,which further corroborates the significance of the phase of the scattering amplitude.展开更多
基金Project supported by the Key Science and Technology Research of Henan Province,China(Grant Nos.162102210111 and 172102310471)the National Key Research and Development Program of China(Grant No.2017YFB0403502)
文摘By numerically solving the time-dependent Schr¨odinger equation, we observe a remarkable strong-field interference pattern in the photoelectron momentum distribution of a hydrogen atom ionized by a few-cycles laser pulse. This interference pattern is joined together with the familiar near-forward strong-field photoelectron holographic interference. By applying the strong-field approximation theory, we investigate the formation of this interference pattern, which arises from the interference between the backward rescattered part and the direct part of the tunneling ionized electron wave packet. We demonstrate that this backward rescattered photoelectron holographic interference can also be observed in a more realistic parallel two-color laser field. These results pave a new way to look into the atomic and molecular structure with ultrafast timescale.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11874163,11604108,and 11604388)the Program for HUST Academic Frontier Youth Teamthe Fundamental Research Funds for the Central Universities,China(HUST No.2017KFXKJC002)。
文摘Coherent superposition of electronic states induces attosecond electron motion in molecules.We theoretically investigate the strong-field ionization of this superposition state by numerically solving the time-dependent Schrodinger equation.In the obtained photoelectron momentum distribution,an intriguing bifurcation structure appears in the strong-field holographic interference pattern.We demonstrate that this bifurcation structure directly provides complete information about the status of the transient wave function of the superposition state:the horizontal location of the bifurcation in the momentum distribution reveals the relative phase of the involved components of the superposition state and the vertical position indicates the relative coefficient.Thus,this bifurcation structure takes a snapshot of the transient electron wave packet of the superposition state and provides an intuitive way to monitor electron motion in molecules.
基金Project supported by the National Natural Science Foundation of China(Gant Nos.12074265,11804233,and 11575118)the National Key Research and Development Project of China(Grant No.2017YFF0106500)+1 种基金the Natural Science Foundation of Guangdong,China(Grant Nos.2018A0303130311 and 2021A1515010082)the Shenzhen Fundamental Research Program(Grant Nos.KQJSCX20180328093801773,JCYJ20180305124540632,and JCYJ20190808121405740).
文摘We develop a numerical scheme for solving the one-dimensional(1D)time-dependent Schrödinger equation(TDSE),and use it to study the strong-field photoionization of the atomic hydrogen.The photoelectron energy spectra obtained for pulses ranging from XUV to near infrared are compared in detail to the spectra calculated with our well-developed code for accurately solving the three-dimensional(3D)TDSE.For XUV pulses,our discussions cover intensities at which the ionization is in the perturbative and nonperturbative regimes.For pulses of 400 nm or longer wavelengths,we distinguish the multiphoton and tunneling regimes.Similarities and discrepancies between the 1D and 3D calculations in each regime are discussed.The observed discrepancies mainly originate from the differences in the transition matrix elements and the energy level structures created in the 1D and 3D calculations.
基金Project supported by the National Key Research and Development Program of China(Grant No.2018YFB1801904)the National Natural Science Foundation of China(Grant No.12075036)the Open Research Fund of National Mobile Communications Research Laboratory,Southeast University(Grant No.2019D14)。
文摘Photoelectron momentum distribution of hydrogen molecular ion in a circularly polarized laser pulse is calculated by solving the three-dimensional time-dependent Schrodinger equation(3D-TDSE).At the intermediate internuclear distance,an unusual multi-peak structure is observed in the angular distribution,which is proved to be a signature of the transient localization of the electron upon alternating nucleus.By tracing the time-dependent ionization rate and bound state populations,we provide a clear evidence that the transient electron localization still exists in circularly polarized pulse and the corresponding multiple ionization bursts are directly mapped onto observable angular distributions.In addition,we introduce an intuitive strong-field approximation model which incorporates laser-induced subcycle internal electron dynamics to isolate the effect of the Coulomb potential of the parent ions.In this way,the timing of each ionization burst can be directly read out from the angular distributions.Our results suggest that the ionization time serves as a sensitive tool encoding intramolecular electron dynamics and can be measured using attoclock technique.
基金This work was supported by the National Key Research and Development Program of China(Grant No.2019YFA0308300)the National Natural Science Foundation of China(Grant Nos.11874163,12021004,11627809,11934006).
文摘Tunneling ionization of atoms and molecules induced by intense laser pulses contains the contributions of numerous quantum orbits.Identifying the contributions of these orbits is crucial for exploring the application of tunneling and for understanding various tunneling-triggered strong-field phenomena.We perform a combined experimental and theoretical study to identify the relative contributions of the quantum orbits corresponding to the electrons tunneling ionized during the adjacent rising and falling quarter cycles of the electric field of the laser pulse.In our scheme,a perturbative second-harmonic field is added to the fundamental driving field.By analyzing the relative phase dependence of the signal in the photoelectron momentum distribution,the relative contributions of these two orbits are unambiguously determined.Our results show that their relative contributions sensitively depend on the longitudinal momentum and modulate with the transverse momentum of the photoelectron,which is attributed to the interference of the electron wave packets of the long orbit.The relative contributions of these orbits resolved here are important for the application of strong-field tunneling ionization as a photoelectron spectroscopy for attosecond time-resolved measurements.
基金supported by the National Key Research and Development Program of China (Grant No. 2019YFA0308300)the National Natural Science Foundation of China (Grant Nos. 11874163, 11934006, and12021004)。
文摘Strong-field tunneling ionization is the first step for a broad class of phenomena in intense laser-atom/molecule interactions. Accurate information about the electron wave packet from strong-field tunneling ionization of atoms and molecules is of essential importance for understanding various tunneling ionization triggered processes. Here, we survey the property of the electron wave packet in tunneling ionization of molecules with a method based on strong-field photoelectron holography. By solving the time-dependent Schr ¨odinger equation, it is shown that the holographic interference in the photoelectron momentum distribution exhibits the asymmetric behavior with respect to the laser polarization direction, when the molecule is aligned with a nonzero angle to the linearly polarized laser field. We demonstrate that this asymmetry is due to the nonzero initial transverse displacement of the electron wave packet at tunneling. By analyzing the holographic interference, this transverse displacement for the launching of electron wave packet tunneling from the molecules is accurately retrieved. This displacement is directly related to the electron density distribution in molecules, and thus our work developed a novel concept for probing electronic structure in molecules.
基金supported by the National Natural Science Foundation of China (Nos.11674243 and 11674242)the State Key Research Program Grant (No.2017YFB1401201)。
文摘The spiderlike structures in the photoelectron momentum distributions of ionized electrons from the hydrogen atom are numerically simulated by using a semiclassical rescattering model(SRM) and solving the time-dependent Schrodinger equation(TDSE),focusing on the role of the phase of the scattering amplitude.With the SRM,we find that the spiderlike legs shift to positions with smaller transverse momentum values while increasing the phase.The spiderlike patterns obtained by SRM and TDSE are in good agreement upon considering this phase.In addition,the time differences in electron ionization and rescattering calculated by SRM and the saddle-point equations are either in agreement or show very similar laws of variation,which further corroborates the significance of the phase of the scattering amplitude.
