Effect of elliptical polarizations on nonsequential double ionization in two-color elliptically polarized laser fields

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.

Dependence of photoelectron-momentum distribution of H_2^+ molecule on orientation angle and laser ellipticity

By numerically solving the two-dimensional time-dependent Schr¨odinger equation under the frozen-nuclei approximation, we are able to study the molecular photoelectron-momentum distribution(MPMD) of H^+_2 with different orientation angles driven by elliptically polarized laser pulse with varying ellipticities. Our numerical results show that the MPMD is sensitive to the orientation angle and the laser ellipticity, which can be explained by the attosecond perturbation ionization theory and the exactly solvable photoionization model. When the ellipticity ε = 0, the final MPMD of x-oriented H^+_2 shows a distinct six-lobe pattern that is different from that with ε = 0.5 and ε = 1. The evolutions of electron wave packet(EWP)and MPMD with x-oriented H^+_2 are presented to interpret this distinct pattern.

Review on typical applications and computational optimizations based on semiclassical methods in strong-field physics

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.

Two-center interference in high-harmonic generation of H2%＋ in a combination of a mid-infrared laser field and a terahertz field

We theoretically investigate the two-center interference in high-order harmonics generated from the H2-＋ in a combination of a mid-infrared laser and a terahertz field by numerically solving the time-dependent Schr ¨odinger equation（TDSE）.The interference minima in high-order harmonic generation（HHG） are effectively suppressed when a THz field is added.The contribution to HHG from the two separate nuclei is used to demonstrate the locating order of the harmonic minima.Furthermore, we also investigate the emission time of harmonics. The results show that the intensity of the short path around 60^th order after adding a THz field is stronger than that in the mid-infrared laser field, which further illustrates the suppression of the interference minima in HHG.

Exploration of strong-field double ionization of C_(3)H_(6) with the structures of propene and cyclopropane in intense laser fields

By using classical ensemble method,we investigate the double ionization of C_(3)H_(6) molecule with different structures(propene and cyclopropane)in intense laser fields.The numerical results show that the non-sequential double ionization occurs in propene molecule rather than cyclopropane molecule in 1200 nm laser field.To further explain this interesting phenomenon,the momentum distribution of double ionized electrons is presented and the result presents the"finger-like"structure at about 30 TW/cm^(2) of propene molecule,and this structure is more obvious than that in cyclopropane molecule.The above phenomena are also demonstrated by analysing the energy distributions of double-ionized electrons versus time.Moreover,we also investigated the angular distribution at the end of pulse,which is different between propene and cyclopropane.

Theoretical study on non-sequential double ionization of carbon disulfide with different bond lengths in linearly polarizedlaser fields

By using a two-dimensional Monte-Carlo classical ensemble method, we investigate the double ionization（DI） process of the CS_2 molecule with different bond lengths in an 800-nm intense laser field. The double ionization probability presents a ＂knee＂ structure with equilibrium internuclear distance R = 2.9245 a.u.（a.u. is short for atomic unit）. As the bond length of CS increases, the DI probability is enhanced and the ＂knee＂ structure becomes less obvious. In addition,the momentum distribution of double ionized electrons is also investigated, which shows the momentum mostly distributed in the first and third quadrants with equilibrium internuclear distance R = 2.9245 a.u. As the bond length of CS increases,the electron momentum becomes evenly distributed in the four quadrants. Furthermore, the energy distributions and the corresponding trajectories of the double-ionized electrons versus time are also demonstrated, which show that the bond length of CS in the CS_2 molecule plays a key role in the DI process.