Quantum state-resolved probing of strong-field-ionized xenon atoms using femtosecond high-order harmonic transient absorption spectroscopy

Femtosecond high-order harmonic transient absorption spectroscopy is used to resolve the complete vertical bar j,m > quantum state distribution of Xe+ produced by optical strong-field ionization of Xe atoms at 800 nm. Probing at the Xe N-4/5 edge yields a population distribution rho(j,vertical bar m vertical bar) of rho(3/2,1/2)rho(1/2,1/2)rho(3/2,3/2)=75 +/- 6 :12 +/- 3 :13 +/- 6%. The result is compared to a tunnel ionization calculation with the inclusion of spin-orbit coupling, revealing nonadiabatic ionization behavior. The sub-50-fs time resolution paves the way for tabletop extreme ultraviolet absorption probing of ultrafast dynamics.