Observation quantum beats of two-photon excited states of Xe atoms with different quantum numbers under photoionization

We studied the photoionization of a coherently two-photon excited superposition of 4$f$ states of Xe atom by probe femtosecond pulse laser in a supersonic beam. The revealed oscillational structure in the photoionization signals is associated with the coherent superposition of two these states. Our results demonstrate the high efficiency of proposed scheme for registering quantum beats. Our scheme is based not on the analysis of results of fluorescence oscillations, but on the observation of oscillations in the photoelectron current.