Electron rescattering in strong-field photodetachment of F⁻

Abstract

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.V-Electron 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 emp...

Intense-Field Multiple-Detachment of F2¯: Competition with Photodissociation

“…Intense laser pulse interactions with atomic and molecular anions are intrinsically different from interactions with overall neutral or positively charged systems. [1][2][3][4][5] For neutral systems, intuitive mechanisms such as tunnel ionization and rescattering can often provide a qualitative, as well as quantitative, description for intense-field processes including above threshold ionization, double ionization and high order harmonic generation (HHG). [6][7][8][9][10][11][12][13] In contrast, far less is known about intense-field interactions with anionic systems.…”

“…Intense laser pulse interactions with atomic and molecular anions are intrinsically different from interactions with overall neutral or positively charged systems. − For neutral systems, intuitive mechanisms such as tunnel ionization followed by rescattering can often provide a qualitative as well as quantitative description for intense-field processes including above-threshold ionization, double ionization, and high-order harmonic generation (HHG). − In contrast, less is known about intense-field interactions with anionic atoms and molecules. Nonsequential processes, including rescattering, were considered to explain the experimentally measured high-energy photoelectron spectra emerging from intense-field interaction with atomic anions. − …”

Intense-Field Double Detachment of Electrostatically Bound F–(NF3)n Cluster Anions

“…Furthermore, once an electron is removed from an anion, its motion is not affected by the attractive Coulomb potential present in initially neutral or cationic systems. Anionic systems can therefore be expected to exhibit new mechanisms of intense-field interaction with matter. − However, despite the progress in understanding intense-field interactions with neutral and cationic systems, far less is known about interactions with anionic systems.…”

Pulse-shape control of two-color interference in high-order-harmonic generation

“…We obtain the harmonic spectra using the ab initio time-dependent R-matrix method known as RMT [18]. RMT has been used to investigate various strongfield phenomena, including multielectron correlation in doubly and core-excited states in Ne [19], electron recollision in F − [20], IR-assisted photoionization of Ne + [21] and HHG from noble gas atoms in the NIR regime [11,22]. A predecessor to the RMT method was also used extensively to study harmonic generation in a variety of targets in the UV-visible range [23][24][25][26].…”