Abstract: Ionization of coherently two-photon-excited superposition of 4f states of Xe in a supersonic atomic beam is studied by means of femtosecond pump–probe spectroscopy. Oscillatory structure in the photoionization signal is related to coherent beats of a superposition of excited states. High efficiency of the proposed scheme of registration of quantum beats was achieved due to nearly 100% efficiency of collecting photoelectrons, in contrast to detection of fluorescence used traditionally.