Enhanced double ionization with circularly polarized light

Gillen, Glen; Walker, Mark A.; Woerkom, L. D. Van

doi:10.1103/physreva.64.043413

Cited by 109 publications

(85 citation statements)

References 27 publications

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“…We believe that also in atoms the first emitted electron may influence the parent ion, such that the averaged ionization probability for the second ionization step is higher than predicted by SDI. An enhanced ion count rate of doubly charged magnesium ions in circularly polarized light has already been reported 20 . However, the count rate statistics of this measurement is insufficient to make an equivalent statement about our measurement.…”

Section: Early Release Of the Second Electronmentioning

confidence: 98%

Timing the release in sequential double ionization

Pfeiffer¹,

Cirelli²,

Smolarski³

et al. 2011

Nature Phys

210

227

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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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Section: Early Release Of the Second Electronmentioning

confidence: 98%

Timing the release in sequential double ionization

Pfeiffer¹,

Cirelli²,

Smolarski³

et al. 2011

Nature Phys

210

227

View full text Add to dashboard Cite

show abstract

“…A particularly sensitive test for the existence of rescattering is a comparison between ion yields obtained using linearly and circularly polarized light. In a circularly polarized field, the electron tends to orbit the core rather than recollide, causing a dramatic suppression of ion yields in double ionization [8].…”

mentioning

confidence: 99%

Evidence for Rescattering in Intense, Femtosecond Laser Interactions with a Negative Ion

et al. 2004

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It is now well established that energetic electron emission, nonsequential ionization, and high harmonic generation, produced during the interaction of intense, femtosecond laser pulses with atoms (and atomic positive ions), can be explained by invoking rescattering of the active electron in the laser field, the so-called rescattering mechanism. In contrast for negative ions, the role of rescattering has not been established experimentally. By irradiating F ÿ ions with ultrashort laser pulses, F ion yields as a function of intensity for both linearly and circularly polarized light have been measured. We find that, at intensities well below saturation for F production by sequential ionization, there is a small but significant enhancement in the yield for the case of linearly polarized light, providing the first clear experimental evidence for the existence of the rescattering mechanism in negative ions.

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“…The seemingly complete lack of a PES plateau region is further discussed in Ref. �12�,where Gillen et al demonstrated that, based on ionization rate ellipticity studies, rescattering does not appear to be as dominant an ionization mechanism for magnesium as it is for the noble gases.…”

Section: A General Pes Characteristicsmentioning

confidence: 97%

Analysis of resonance structure in the above-threshold ionization photoelectron spectra of magnesium

Gillen

Woerkom

2003

Phys. Rev. A

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Using high-resolution photoelectron spectroscopy and 120-fs, 800-nm Ti:sapphire laser pulses, we observe and analyze intensity-dependent resonant population of specific intermediate excited states of neutral magne sium atoms and their subsequent photoionization in the laser field. Various participating states are identified using angular-momentum selection rules, partial yields, and angular distributions. Several unexpected results are observed and discussed, including peaks that do not correspond to expected resonant processes, and order-to-order variations in the photoelectron spectra.

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Enhanced double ionization with circularly polarized light

Cited by 109 publications

References 27 publications

Timing the release in sequential double ionization

Timing the release in sequential double ionization

Evidence for Rescattering in Intense, Femtosecond Laser Interactions with a Negative Ion

Analysis of resonance structure in the above-threshold ionization photoelectron spectra of magnesium

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