Retrieving photorecombination cross sections of atoms from high-order harmonic spectra

Abstract

We observe high-order harmonic spectra generated from a thin atomic medium, Ar, Kr, and Xe, by intense $800\text{−}\mathrm{nm}$ and $1300\text{−}\mathrm{nm}$ femtosecond pulses. A clear signature of a single-atom response is observed in the harmonic spectra. Especially in the case of Ar, a Cooper minimum, reflecting the electronic structure of the atom, is observed in the harmonic spectra. We successfully extract the photorecombination cross sections of the atoms in the field-free condition with the help of an accurate recolliding electron wave packet. The present protocol paves the way for exploring ultrafast imaging of molecular dynamics with attosecond resolution.