Nonsequential double ionization with mid-infrared laser fields

Abstract

Using a full-dimensional Monte Carlo classical ensemble method, we present a theoretical study of atomic nonsequential double ionization (NSDI) with mid-infrared laser fields, and compare with results from near-infrared laser fields. Unlike single-electron strong-field processes, double ionization shows complex and unexpected interplays between the returning electron and its parent ion core. As a result of these interplays, NSDI for mid-IR fields is dominated by second-returning electron trajectories, instead of first-returning trajectories for near-IR fields. Some complex NSDI channels commonly happen with near-IR fields, such as the recollision-excitation-with-subsequent-ionization (RESI) channel, are virtually shut down by mid-IR fields. Besides, the final energies of the two electrons can be extremely unequal, leading to novel e-e momentum correlation spectra that can be measured experimentally.

H2: the benchmark molecule for ultrafast science and technologies

“…Modeling the combined electron-nuclear dynamics in H 2 with quantum [87][88][89] and classical models [90] allowed a detailed analysis of the NSDI mechanisms such as multiple recollisions, and recollision induced excitation. Furthermore, theory specifically addressed NSDI in few-cycle optical pulses [91,92], the alignment dependence of NSDI [93][94][95] and its wavelength dependence [96].…”

Universal time delay in the recollision impact ionization pathway of strong-field nonsequential double ionization

“…In our case, the two electrons escape one after the other, and thus the ionization time is responsible. Figure 6 shows the separated CEMDs for a higher recollision energy (with = U 0.69 In the multicycle laser fields, the recollision repeats every half cycle, and there are many NSDI events where recollisions occur at the second and third returns [37,38,53]. The NSDI signals are the composite contribution of these trajectories.…”

The Coulomb effect in nonsequential double ionization by counter-rotating two-color elliptical polarization fields

“…What one is interested in is the electron correlation behavior in NSDI and responsible ultrafast dynamics processes for those behaviors. [17][18][19][20][21][22][23][24][25] In linearly polarized laser fields, the released electron mainly moves in one direction driven by the laser electric field. The motion of the electron is simple and the recollision probability with the parent ion is relatively high.…”