Electron detachment from negative ions in a short laser pulse

Shearer, S. F. C.; Smyth, Maeve; Gribakin, G. F.

doi:10.1103/physreva.84.033409

Cited by 17 publications

(63 citation statements)

References 15 publications

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“…The laser parameters are chosen to facilitate a comparison with results obtained using a Keldysh-Type Approach (KTA) calculation [14,23,24]. In this model, the effect of the atomic potential on a detached electron is neglected.…”

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confidence: 99%

Electron rescattering in strong-field photodetachment ofF−

et al. 2015

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We present ab initio studies of photoelectron spectra for above threshold detachment (ATD) of F − anions in short, 1300 nm and 1800 nm laser pulses. We identify and assess the importance of electron rescattering in strong-field photodetachment of a negative ion through comparison with an analytic, Keldysh-type approach, demonstrating the capability of ab-initio computation in the challenging near-IR regime. We further assess the influence of the strong electron correlation on the photodetachment.PACS numbers: 32.80.Gc 31.15.VElectron rescattering is one of the fundamental processes occuring in the interaction between matter and intense light fields [1]. The mechanism is a critical part of the well known three-step or recollision model for high harmonic generation (HHG) or strong field double ionisation. According to the model an electron is first ionised, then driven by a strong laser field, before recolliding with the parent ion, either recombining, leading to HHG [2,3], or rescattering, leading to high-energy electron emission [4,5], or non-sequential double ionisation [6].Electron rescattering also encodes structural information about the residual ion into the wavepacket of the ejected electron and can thus be exploited as an experimental probe of the structure of the parent ion [1]. The technique is especially sensitive as the current density of a recolliding electron wavepacket exceeds that of conventional electron sources by several orders of magnitude [7]. Furthermore, the inherently subcycle and phase-locked nature of the recollision process gives access to electron dynamics on the attosecond scale, via information embedded in the photoelectron spectrum [8,9].One of the open questions in strong-field science concerns the importance of electron rescattering for negative ions. Significant progress has been made in understanding and controlling the equivalent process in neutral atoms and positive ions [10], but above-threshold detachment (ATD) presents a different challenge. The small binding energy allows detachment at low intensities. Hence to reach significant recollision energies, nearinfrared (NIR) laser fields are required. In addition, the absence of the Coulomb potential makes it easier for the electron wavepacket to spread out, reducing the effect of rescattering [4,5]. While evidence for rescattering from negative ions has been found experimentally [11], no verification has yet been provided from ab initio theory. A theoretical approach, based on first order correction to the strong field approximation, was able to reproduce experimental results from Br − and F − , [12] but a more recent study, using a numerical solution of the time-dependent Schrödinger equation (TDSE), found "no qualitative evidence of rescattering" for H − [13]. In this report we demonstrate that ab-initio theory can be used to investigate rescattering in the NIR regime.An additional complication in the description of negative ions is the much larger influence of dielectronicrepulsion. Several approximate methods have been empl...

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Electron rescattering in strong-field photodetachment ofF−

et al. 2015

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“…The PADs show a two-peak structure, which has been both experimentally observed and theoretically predicted in the H − and X − (X = F, Br) anion systems. [6][7][8]18,19 Using the method mentioned above, we calculated these three-photon detachment processes and compare them with the experimental results. On the basis of LOPT, the detached electron can be in either a p or f state in the case of three-photon detachment.…”

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Femtosecond Photodetachment of Silver Anions

Liu

Long²,

Wang³

et al. 2013

J. Phys. Chem. A

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ABSTRACT:The two-and three-photon detachment of negative silver ions in a femtosecond infrared laser field is studied using photoelectron velocity map imaging methods. Photoelectron angular distributions (PADs) are obtained for these detachment channels; these PADs change dramatically when the laser wavelength and intensity are changed. Theoretical predictions, which are based on the adiabatic Keldysh−Faisal−Reiss saddle point method, are in good agreement with our experiment. The dependence of the PAD on the laser wavelengths and intensities is due to the interference between the different partial wave functions. The relative contributions of the different partial waves to the detachment amplitude are altered by changing the laser parameters and, as a result, the shape of the PAD. Close to the detachment threshold, the two-photon detachment process also follows the Wigner threshold law. Near the detachment threshold, the large differences between the calculated results and our experimental results indicate that the ponderomotive energy shifts caused by the femtosecond laser fields must be taken into account in the theoretical model. The three-photon detachment of Ag − is also observed and compared with theoretical calculations.

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“…Depending on the pump pulse length, strongfield detachment may not generally produce perfectly coherent aligned states. The elements of the density matrix in the |J,M basis can be determined by calculating the detachment amplitudes for a variety of pulse lengths using existing theory of strong-field photodetachment (e.g., Keldysh-type theory [11,[13][14][15][16]). In this approach the diagonal elements will represent populations of different atomic fine-structure levels for a given M, and the magnitude of the off-diagonal elements will describe coherences between the J states.…”

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Dynamics of atomic spin-orbit-state wave packets produced by short-pulse laser photodetachment

Law

Gribakin

2016

Phys. Rev. A

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We analyse the experiment by Hultgren et al. [Phys. Rev. A 87, 031404 (2013)] on orbital alignment and quantum beats in coherently excited atomic fine-structure manifolds produced by short-pulse laser photodetachment of C − , Si − and Ge − negative ions, and derive a formula that describes the beats. Analysis of the experimental data enables us to extract the non-coherent background contribution for each species, and indicates the need for a full density matrix treatment of the problem.

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Electron detachment from negative ions in a short laser pulse

Cited by 17 publications

References 15 publications

Electron rescattering in strong-field photodetachment ofF−

Electron rescattering in strong-field photodetachment ofF−

Femtosecond Photodetachment of Silver Anions

Dynamics of atomic spin-orbit-state wave packets produced by short-pulse laser photodetachment

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