Perspectives of Ramsey schemes based on high-order harmonics for high-resolution XUV spectroscopy

We present an experimental and theoretical investigation of Ramsey-type interference fringes using high-order harmonic generation. The ninth harmonic (lambda = 88nm) of a femtosecond Ti:sapphire laser was used to excite a pair of autoionizing states of krypton. The outcome of the ionization process, detected by an ion-mass spectrometer, shows the characteristic quantum interference pattern. The behavior of the fringe contrast was interpreted on the basis of a simple analytical model, which reproduced well the experimental results without any free parameter. Finally, we also present a proposal for a similar experiment to be performed on high-lying bound state of atomic argon, with the aim of achieving even higher resolving power.