Fig. 1: RABBITT sideband principle and energy resolution in attosecond PES experiments.
From: Attosecond intra-valence band dynamics and resonant-photoemission delays in W(110)
a An IR-probe field gives rise to sidebands between separated high-harmonic peaks in a photoelectron spectrum. Each sideband SB2m can be reached by absorption of an XUV photon of the two neighboring high harmonics HH2m±1 and the absorption/emission of an IR photon. Because of interference between the two possible paths, the sideband intensity oscillates as a function of the pump–probe delay and gives access to the photoemission timing. b Photoelectron spectra from two discrete electronic states A and B excited with a single isolated attosecond pulse (left) and a train of attosecond pulses (right) with the same spectral envelope. The broad continuous spectrum of the isolated pulse makes the photoelectrons from the closely neighbored states largely overlap. In contrast, the narrow and well-separated high harmonics of a pulse train enable a distinction between the photoemission from the two initial states. c Schematic representation of space-charge broadening: photoelectrons are released by an attosecond pulse train from a two-state system as in a. The repulsive electrostatic force between the photoelectrons leads to space-charge broadening and smears out the fine structure of the photoelectron spectrum.
