%0 Journal Article
%T Modulation of attosecond beating in resonant two-photon ionization
%A ¨¢lvaro J. Gal¨¢n
%A Luca Argenti
%A Fernando Mart¨ªn
%J Physics
%D 2014
%I arXiv
%R 10.1103/PhysRevLett.113.263001
%X We present a theoretical study of the photoelectron attosecond beating at the basis of RABBIT (Reconstruction of Attosecond Beating By Interference of Two-photon transitions) in the presence of autoionizing states. We show that, as a harmonic traverses a resonance, its sidebands exhibit a peaked phase shift as well as a modulation of the beating frequency itself. Furthermore, the beating between two resonant paths persists even when the pump and the probe pulses do not overlap, thus providing a sensitive non-holographic interferometric means to reconstruct coherent metastable wave packets. We characterize these phenomena quantitatively with a general finite-pulse analytical model that accounts for the effect of both intermediate and final resonances on two-photon processes, at a negligible computational cost. The model predictions are in excellent agreement with those of accurate ab initio calculations for the helium atom in the region of the N=2 doubly excited states.
%U http://arxiv.org/abs/1405.4732v1