Perspectives of Ramsey Schemes Based on High Order Harmonics for High- Resolution XUV Spectroscopy

We present an experimental and theoretical investigation of Ramseytype interference fringes using highorder harmonic generation. The ninth harmonic (λ 88 nm) 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 ionmass 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 experi mental results without any free parameter. Finally, we also present a proposal for a similar experiment to be performed on highlying bound state of atomic argon, with the aim of achieving even higher resolving power.