Based on NII spectra, some transition probabilities for 2p4f-2p3d and 2s2p23d-2s2p23p are obtained by a semi- classical method. The results are in good agreement with other measurements and the data reported by the Na...Based on NII spectra, some transition probabilities for 2p4f-2p3d and 2s2p23d-2s2p23p are obtained by a semi- classical method. The results are in good agreement with other measurements and the data reported by the National Institute of Standards and Technology. The transition probability for a line of 424.18nm is reported for the first time. Meanwhile, a feasible method of calculating transition parameters related to special excited configurations or highly excited states is provided.展开更多
The semiclassical method based on Feynman’s path-integral is in favor of uncovering the quantum tunneling effect,the classical trajectory description of the electron, and the quantum phase information, which can pres...The semiclassical method based on Feynman’s path-integral is in favor of uncovering the quantum tunneling effect,the classical trajectory description of the electron, and the quantum phase information, which can present an intuitive and transparent physical image of electron’s propagation in comparison with the ab initio time-dependent Schr ¨odinger equation.In this review, we introduce the basic theoretical concepts and development of several semiclassical methods as well as some of their applications in strong-field physics. Special emphasis is placed on extracting time delay on attosecond scale by the combination of the semiclassical method with phase of phase method. Hundreds of millions of trajectories are generally adopted to obtain a relatively high-resolution photoelectron spectrum, which would take a large amount of time. Here we also introduce several optimization approaches of the semiclassical method to overcome the time-consuming problem of violence calculation.展开更多
We investigate atomic above-threshold ionization in elliptically polarized strong laser fields with a semiclassical approach.With increasing laser intensity,the Coulomb focusing（CF） effects are found to become stron...We investigate atomic above-threshold ionization in elliptically polarized strong laser fields with a semiclassical approach.With increasing laser intensity,the Coulomb focusing（CF） effects are found to become stronger in both parallel and perpendicular directions with respect to the polarization plane.The dependence of CF effects on tunnel exit,initial transverse momentum distribution and laser electric field is analyzed.It was revealed that the effects of tunnel exit are most prominent with variation of the laser intensity,and the other two factors both play non-negligible roles.Our results provide a deeper insight to the recent experiments of Coulomb asymmetry[Shafir D,et al.,2013 Phys.Rev.Lett.111 023005 and Li M,et al,2013 Phys.Rev.Lett.111 023006].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 propose a procedure to generalize the Husimi distribution to systems with continuous spectrum. We start examining a pioneering work, by Gazeau and Klauder, where the concept of coherent states for systems with disc...We propose a procedure to generalize the Husimi distribution to systems with continuous spectrum. We start examining a pioneering work, by Gazeau and Klauder, where the concept of coherent states for systems with discrete spectrum was extended to systems with continuous one. In the present article, we see the Husimi distribution as a representation of the density operator in terms of a basis of coherent states. There are other ways to obtain it, but we do not consider here. We specially discuss the problem of the continuous harmonic oscillator.展开更多
A semiclassical lattice Boltzmann method is presented for axisymmetric flows of gas of particles of arbitrary statistics.The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations...A semiclassical lattice Boltzmann method is presented for axisymmetric flows of gas of particles of arbitrary statistics.The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations in twodimensional rectangular coordinates onto the tensor Hermite polynomials using moment expansion method and then the forcing strategy of Halliday et al.(Phys.Rev.E.,64(2001),011208)is adopted and forcing term is added into the resulting microdynamic evolution equation.The determination of the forcing terms is dictated by yielding the emergent macroscopic equations toward a particular target form.The correct macroscopic equations of the incompressible axisymmetric viscous flows are recovered through the Chapman-Enskog expansion.Computations of uniform flow over a sphere to verify the method are included.The results also indicate distinct characteristics of the effects of quantum statistics.展开更多
Computations of microscopic circular pipe flow in a rarefied quantum gas are presented using a semiclassical axisymmetric lattice Boltzmann method.The method is first derived by directly projecting the Uehling-Uhlenbe...Computations of microscopic circular pipe flow in a rarefied quantum gas are presented using a semiclassical axisymmetric lattice Boltzmann method.The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations in two-dimensional rectangular coordinates onto the tensor Hermite polynomials using moment expansion method and then the forcing strategy of Halliday et al.[Phys.Rev.E.,64(2001),011208]is adopted by adding forcing terms into the resulting microdynamic evolution equation.The determination of the forcing terms is dictated by yielding the emergent macroscopic equations toward a particular target form.The correct macroscopic equations of the incompressible axisymmetric viscous flows are recovered through the Chapman-Enskog expansion.The velocity profiles and the mass flow rates of pipe flows with several Knudsen numbers covering different flow regimes are presented.It is found the Knudsen minimum can be captured in all three statistics studied.The results also indicate distinct characteristics of the effects of quantum statistics.展开更多
We investigate possible ways in which a quantum wavepacket spreads. We show that in a general class of double kicked rotor system, a wavepacket may undergo superballistic spreading; i.e., its variance increases as the...We investigate possible ways in which a quantum wavepacket spreads. We show that in a general class of double kicked rotor system, a wavepacket may undergo superballistic spreading; i.e., its variance increases as the cubic of time. The conditions for the observed superballistic spreading and two related characteristic time scales are studied. Our results suggest that the symmetry of the studied model and whether it is a Kolmogorov-Arnold-Moser system are crucial to its wavepacket spreading behavior. Our study also sheds new light on the exponential wavepacket spreading phenomenon previously observed in the double kicked rotor system.展开更多
基金Project supported by the National Natural Science Foundation of China （Grant No 40475007）.
文摘Based on NII spectra, some transition probabilities for 2p4f-2p3d and 2s2p23d-2s2p23p are obtained by a semi- classical method. The results are in good agreement with other measurements and the data reported by the National Institute of Standards and Technology. The transition probability for a line of 424.18nm is reported for the first time. Meanwhile, a feasible method of calculating transition parameters related to special excited configurations or highly excited states is provided.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.91950101,12074240,and 12104285)Sino-German Mobility Programme(Grant No.M0031)+1 种基金the High Level University Projects of the Guangdong Province,China(Mathematics,Shantou University)the Open Fund of the State Key Laboratory of High Field Laser Physics(SIOM)。
文摘The semiclassical method based on Feynman’s path-integral is in favor of uncovering the quantum tunneling effect,the classical trajectory description of the electron, and the quantum phase information, which can present an intuitive and transparent physical image of electron’s propagation in comparison with the ab initio time-dependent Schr ¨odinger equation.In this review, we introduce the basic theoretical concepts and development of several semiclassical methods as well as some of their applications in strong-field physics. Special emphasis is placed on extracting time delay on attosecond scale by the combination of the semiclassical method with phase of phase method. Hundreds of millions of trajectories are generally adopted to obtain a relatively high-resolution photoelectron spectrum, which would take a large amount of time. Here we also introduce several optimization approaches of the semiclassical method to overcome the time-consuming problem of violence calculation.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11547218,11564020,and 11504314)
文摘We investigate atomic above-threshold ionization in elliptically polarized strong laser fields with a semiclassical approach.With increasing laser intensity,the Coulomb focusing（CF） effects are found to become stronger in both parallel and perpendicular directions with respect to the polarization plane.The dependence of CF effects on tunnel exit,initial transverse momentum distribution and laser electric field is analyzed.It was revealed that the effects of tunnel exit are most prominent with variation of the laser intensity,and the other two factors both play non-negligible roles.Our results provide a deeper insight to the recent experiments of Coulomb asymmetry[Shafir D,et al.,2013 Phys.Rev.Lett.111 023005 and Li M,et al,2013 Phys.Rev.Lett.111 023006].
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partial financial support by FONDECYT, under Grant No. 1080487
文摘We propose a procedure to generalize the Husimi distribution to systems with continuous spectrum. We start examining a pioneering work, by Gazeau and Klauder, where the concept of coherent states for systems with discrete spectrum was extended to systems with continuous one. In the present article, we see the Husimi distribution as a representation of the density operator in terms of a basis of coherent states. There are other ways to obtain it, but we do not consider here. We specially discuss the problem of the continuous harmonic oscillator.
基金supported by CQSE Subproject#597R0066-69 and NSC 97-2221-E002-063-MY3They also acknowledge the support of NCHC in providing resource under the national project “Knowledge Innovation National Grid”in Taiwan are acknowledged.
文摘A semiclassical lattice Boltzmann method is presented for axisymmetric flows of gas of particles of arbitrary statistics.The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations in twodimensional rectangular coordinates onto the tensor Hermite polynomials using moment expansion method and then the forcing strategy of Halliday et al.(Phys.Rev.E.,64(2001),011208)is adopted and forcing term is added into the resulting microdynamic evolution equation.The determination of the forcing terms is dictated by yielding the emergent macroscopic equations toward a particular target form.The correct macroscopic equations of the incompressible axisymmetric viscous flows are recovered through the Chapman-Enskog expansion.Computations of uniform flow over a sphere to verify the method are included.The results also indicate distinct characteristics of the effects of quantum statistics.
基金supported by CQSE Subproject#597R0066-69 and NSC 97-2221-E002-063-MY3support of NCHC in providing resource under the national project"Knowledge Innovation National Grid"in Taiwan are acknowledged.
文摘Computations of microscopic circular pipe flow in a rarefied quantum gas are presented using a semiclassical axisymmetric lattice Boltzmann method.The method is first derived by directly projecting the Uehling-Uhlenbeck Boltzmann-BGK equations in two-dimensional rectangular coordinates onto the tensor Hermite polynomials using moment expansion method and then the forcing strategy of Halliday et al.[Phys.Rev.E.,64(2001),011208]is adopted by adding forcing terms into the resulting microdynamic evolution equation.The determination of the forcing terms is dictated by yielding the emergent macroscopic equations toward a particular target form.The correct macroscopic equations of the incompressible axisymmetric viscous flows are recovered through the Chapman-Enskog expansion.The velocity profiles and the mass flow rates of pipe flows with several Knudsen numbers covering different flow regimes are presented.It is found the Knudsen minimum can be captured in all three statistics studied.The results also indicate distinct characteristics of the effects of quantum statistics.
基金supported by the National Natural Science Foundation of China(Grants Nos.11275159,11535011 and 11335006)
文摘We investigate possible ways in which a quantum wavepacket spreads. We show that in a general class of double kicked rotor system, a wavepacket may undergo superballistic spreading; i.e., its variance increases as the cubic of time. The conditions for the observed superballistic spreading and two related characteristic time scales are studied. Our results suggest that the symmetry of the studied model and whether it is a Kolmogorov-Arnold-Moser system are crucial to its wavepacket spreading behavior. Our study also sheds new light on the exponential wavepacket spreading phenomenon previously observed in the double kicked rotor system.
