Strong-field effects in the photoemission spectrum of theC60fullerene

Abstract

Considering C60 as a model system for describing field emission from the extremity of a carbon nanotip, we explore electron emission from this fullerene excited by an intense, near-infrared, fewcycle laser pulse (10 13 -10 14 W/cm 2 , 912 nm, 8-cycle). To this end, we use time-dependent density functional theory augmented by a self-interaction correction. The ionic background of C60 is described by a soft jellium model. Particular attention is paid to the high energy electrons. Comparing the spectra at different emission angles, we find that, as a major result of this study, the photoelectrons are strongly peaked along the laser polarization axis forming a highly collimated electron beam in the forward direction, especially for the high energy electrons. Moreover, the high-energy plateau cut-off found in the simulations agrees well with estimates from the classical three-step model. We also investigate the build-up of the high-energy part of a photoelectron spectrum by a time-resolved analysis. In particular, the modulation on the plateau can be interpreted as contributions from intracycle and intercycle interferences.

Forward-backward asymmetry of photoemission inC60excited by few-cycle laser pulses

“…The other parameters are the same as those in Ref. [32]. With the present scheme, we reproduce rather well the electronic properties of C 60 : an IP at E IP = 7.62 eV, a HOMO-LUMO gap of 1.77 eV, and a reasonable description of the photoabsorption spectrum [45].…”

“…From a geometrical point of view, C 60 is similar to the outermost part of capped-carbon nanotips which are promising XUV electron nanoemitters. In a previous work [32], we have theoretically investigated the PES of C 60 in strong fields using a near-infrared laser pulse (λ las =912 nm). In that study, CEP effects were neglected since we considered comparatively long pulses comprising about 8 optical cycles.…”

“…Our modeling is based on Time-Dependent Density-Functional Theory [34] with the time-dependent local-density approximation using the jellium approximation for the ionic background [32]. We will focus on the dependence of the CEP effect on pulse length and on the forward-backward asymmetry of photoemission due to electron rescattering.…”

Efficient and accurate modeling of electron photoemission in nanostructures with TDDFT

“…Following Ref. [70], we consider the fullerene C 60 exposed to a strong laser pulse, linearly polarized along the z-axis with frequency ω = 1.36 eV, intensity I = 10 14 W/cm 2 , and pulse length T pulse = 24 fs. In Ref.…”

“…In Ref. [70] the positively charged ionic background of the molecule was approximated by a jellium shell and calculations where performed in cylindrical coordinates. As already mentioned in the reference, this model suffers from the fact that returning electrons collide with a jellium well instead of a carbon ion which eventually leads to an underestimation of high-energy electrons.…”