Complete characterization of single-cycle double ionization of argon from the nonsequential to the sequential ionization regime

Abstract

Selected features of nonsequential double ionization have been qualitatively reproduced by a multitude of different (quantum and classical) approaches. In general, however, the typical uncertainty of laser pulse parameters and the restricted number of observables measured in individual experiments leave room for adjusting theoretical results to match the experimental data. While this has been hampering the assessment of different theoretical approaches leading to conflicting interpretations, comprehensive experimental data that would allow such an ultimate and quantitative assessment have been missing so far. To remedy this situation we have performed a kinematically complete measurement of single-cycle multiple ionization of argon over a one order of magnitude range of intensity. The momenta of electrons and ions resulting from the ionization of the target gas are measured in coincidence, while each ionization event is tagged with the carrier-envelope phase and intensity of the 4-fs laser pulse driving the process. The acquired highly differential experimental data provide a benchmark for a rigorous test of the many competing theoretical models used to describe nonsequential double ionization.

Phase- and intensity-dependence of ultrafast dynamics in hydrocarbon molecules in few-cycle laser fields

“…Characterizing the ionization process provides valuable information on the field-driven molecular dynamics. Very recently, it has been demonstrated for argon that the combined intensity and CEP dependence of double ionization allows characterizing the underlying mechanisms [42]. Here, we extend this technique to molecular double ionization.…”

“…Since pulse duration and focusing geometry of the laser pulses remain unaffected by the ND filter setting, the measured laser power is directly proportional to the intensity in the laser focus. The proportionality factors between the laser intensity and pulse energy are determined in separate measurements on Ar and Ne targets [42]. The data recorded with the REMI are correlated with both the simultaneously measured CEP and power of the laser pulses in order to access the CEP and intensity-dependence of the deprotonation,…”

Recollision as a probe of magnetic-field effects in nonsequential double ionization

“…Thus, in the 3D-SMND model non-dipole effects are fully accounted for in the two-electron dynamics. Some of the successes of the 3D-SMD model are identifying the mechanism responsible for the fingerlike structure [17], which was predicted theoretically [18] and was observed experimentally for He driven by 800 nm laser fields [19,20]; investigating direct versus delayed pathways of NSDI for He driven by a 400 nm laser field while achieving excellent agreement with fully ab-initio quantum mechanical calculations [21]; identifying the underlying mechanisms for the carrierenvelope phase effects observed experimentally in NSDI of Ar driven by an 800 nm laser field at a range of intensities [22,23]. The 3D-SMD model is extended to the 3D-SMND model employed in the current work to fully account for the magnetic field during time propagation.…”

Compact and flexible harmonic generator and three-color synthesizer for femtosecond coherent control and time-resolved studies

“…We find best agreement with the momentum shifts observed in the experiments when the intensities used in the simulation are 3 times higher than the experimentally retrieved intensities. The fact that electron momenta are systematically underestimated in a semi-classical approach is known (see for instance [50,51]). We note that the simple model cannot capture all details of the process, however we like to emphasize that a higher-level of theory was not essential here, since the results rather serve to demonstrate the capabilities of the waveform synthesizer.…”