Correlated Multielectron Dynamics in Ultrafast Laser Pulse Interactions with Atoms

Rudenko, Artem; Zrost, K.; Feuerstein, B.; Jesus, V. L. B. de; Schröter, C. D.; Moshammer, R.; Ullrich, J.

doi:10.1103/physrevlett.93.253001

Cited by 177 publications

(137 citation statements)

References 21 publications

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“…Averaged over the CEP, this results in the crossshaped structures seen in Figs 1a and 2b. This finding is in contrast to the common assumption that the second electron in the RESI mechanism is released at the peak of the electric field and acquires a small momentum distributed around zero 7 . Multiple recollision events, which occur in the several-to-multicycle regime, severely hamper the interpretation of measured correlation spectra.…”

Section: Discussioncontrasting

confidence: 96%

“…The well-known concept of attosecond streaking spectroscopy has permitted the observation of singleelectron dynamics with attosecond time resolution 4 . Despite this progress, however, the ultrafast dynamics of multiple electrons has resisted direct observation, even though far-reaching conclusions were drawn from kinematically complete strong-field double 5,6 and multiple ionization 7 experiments.…”

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Attosecond tracing of correlated electron-emission in non-sequential double ionization

et al. 2012

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Despite their broad implications for phenomena such as molecular bonding or chemical reac tions, our knowledge of multi electron dynamics is limited and their theoretical modelling remains a most difficult task. From the experimental side, it is highly desirable to study the dynamical evolution and interaction of the electrons over the relevant timescales, which extend into the attosecond regime. Here we use near single cycle laser pulses with well defined electric field evolution to confine the double ionization of argon atoms to a single laser cycle. The measured two electron momentum spectra, which substantially differ from spectra recorded in all previous experiments using longer pulses, allow us to trace the correlated emission of the two electrons on sub femtosecond timescales. The experimental results, which are discussed in terms of a semiclassical model, provide strong constraints for the development of theories and lead us to revise common assumptions about the mechanism that governs double ionization.

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Section: Discussioncontrasting

confidence: 96%

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Attosecond tracing of correlated electron-emission in non-sequential double ionization

et al. 2012

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“…Two further observations strongly support such an interpretation: First, using shorter pulses, i.e., reducing the number of recollisions the RESI mechanism was demonstrated to become less efficient [28], subsequent recollisional heating is suppressed. Second, the similarity in shape between the high-energy tails of the electron's sum-energy spectrum for Ar 2 and the Ar 1 ATI plateau [see Fig.…”

Section: 053001 (2008) P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 83%

Strong-Field Double Ionization of Ar below the Recollision Threshold

et al. 2008

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Nonsequential double ionization of Ar by 45 fs laser pulses (800 nm) at 4-7 10 13 W=cm 2 was explored in fully differential measurements. Well below the field-modified recollision threshold we enter the multiphoton regime. Strongly correlated back-to-back emission of the electrons along the polarization direction is observed to dominate in striking contrast to all previous data. No effect of Coulomb repulsion can be found, the predicted cutoff in the sum-energy spectra of two emitted electrons is confirmed, and the potential importance of multiple recollisions is discussed. DOI: 10.1103/PhysRevLett.101.053001 PACS numbers: 32.80.Rm, 31.90.+s, 32.80.Fb, 32.80.Wr Within the past three decades extensive studies on the interaction of intense laser fields with atoms and molecules have resulted in a profound understanding of various strong-field phenomena. Prominent examples are abovethreshold ionization (ATI) [1] or high-order harmonic generation [2], both essentially treatable within the single active electron (SAE) approximation. Correlated fewelectron processes, on the other hand, most important, for example, in nonsequential double (multiple) ionization (NSDI) (for a recent review see, e.g., [3]) have, until the present day, resisted any comprehensive modeling.Recently, however, a breakthrough was achieved at high intensities ( PW=cm 2 ) [4]. The application of many-particle imaging techniques [reaction microscopes and cold target recoil ion momentum spectroscopy (COLTRIMS)] [5] has allowed recording (multi)differential data on strong-field few-electron reactions and sophisticated calculations (see, e.g., [6] and references therein) have advanced their theoretical interpretation. As a result, a commonly accepted though simple picture has emerged, characterizing NSDI. Here an electron first tunnels into the field, is then accelerated, and finally thrown back onto its parent ion by the oscillating laser field. During ''recollision'' n-fold ionization might occur either in a direct e; ne -like encounter or indirectly via recollision-induced excitation of the ion plus subsequent field ionization (RESI) [7]. Signatures of the former are that both electrons are exclusively emitted into the same hemisphere along the polarization direction leading to ''double-hump'' shaped parallel momentum distributions of the ions (compensating the electron momenta). For RESI instead, according to the present understanding, the electrons can be emitted either parallel or back to back, thus filling the valley in between the double hump for the ions. Beyond the well-accepted simple scenario, however, major questions about the correlated electron emission are still far from being understood and are extensively investigated [6,8] because recollision is at the very heart of attoscience, molecular tomography, or imaging [9].At low intensities one intriguing though still widely unexplored question did arise early on within the above picture [10]. What happens when the energy of the recolliding electron of up to 3:17U P is not sufficient t...

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“…With linearly polarized fields in strong-field double ionization the dominating ionization mechanism is induced by recollision of the first emitted electron 3,4 . With close-to-circular polarization, however, we can avoid this recollision and therefore investigate a conceptually even simpler process of few-body quantum mechanics.…”

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Timing the release in sequential double ionization

Pfeiffer¹,

Cirelli²,

Smolarski³

et al. 2011

Nature Phys

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The timing of electron release in strong-field double ionization poses great challenges both for conceptual definition and for conducting experimental measurements. Here we present coincidence momentum measurements of the doubly charged ion and of the two electrons arising from double ionization of argon using elliptically polarized laser pulses. Based on a semi-classical model, the ionization times are calculated from the measured electron momenta across a large intensity range. This paper discusses how this method provides timings on a coarse and on a fine scale, similar to the hour and the minute hand of a clock. We found that the ionization time of the first electron is in good agreement with the simulation, whereas the ionization of the second electron occurs significantly earlier than predicted.A mong all the methods used to measure time, one of the most fundamental is to measure the angle of a rotating hand, such as is done on an analogue watch face. This principle can be employed in strong-field ionization using laser pulses with close-to-circular polarization. In the attoclock the rotating electric field vector is used to deflect photo-ionized electrons, such that the instant of ionization is mapped to the final angle of the momentum, similar to the minute hand of a clock. The attoclock technique is based on the definition of 'time' by 'counting cycles' 1,2 . During one period the watch hand completes one cycle, such that measuring the emission angle of the electron enables us to measure time at a precision well below one optical period 2 . Thus the measurement provides attosecond timing without using an attosecond pulse.Here we use the attoclock to measure the ionization times of the two electrons in the double ionization of argon. As a result of depletion the averaged ionization time of the electrons is shifted towards the beginning of the pulse, thus requiring a multi-cycle measurement. The magnitude of the electron momenta follows the envelope of the laser pulse and gives a coarse timing for the electron release (that is 'the hour hand of the clock'). The emission angle of the electrons subsequently gives the fine timing (that is 'the minute hand of the clock').The result of the attoclock measurements addresses a fundamental question in double ionization: are there electron correlation mechanisms that are not induced by recollision? With linearly polarized fields in strong-field double ionization the dominating ionization mechanism is induced by recollision of the first emitted electron 3,4 . With close-to-circular polarization, however, we can avoid this recollision and therefore investigate a conceptually even simpler process of few-body quantum mechanics.It is impossible, at present, to simulate this process based on the time dependent Schrödinger equation (TDSE) because of exceedingly large computing time requirements 5 . Instead one describes the process usually in terms of simplifying mechanisms, which can be classified as sequential double ionization (SDI) or non-sequential double ionization ...

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Correlated Multielectron Dynamics in Ultrafast Laser Pulse Interactions with Atoms

Cited by 177 publications

References 21 publications

Attosecond tracing of correlated electron-emission in non-sequential double ionization

Attosecond tracing of correlated electron-emission in non-sequential double ionization

Strong-Field Double Ionization of Ar below the Recollision Threshold

Timing the release in sequential double ionization

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