Ramsey-type spectroscopy with high-order harmonics

Ramsey type spectroscopy was applied to autoionizing states of krypton, using the ninth harmonic of a Ti:sapphire laser. The electrons produced by the photoionization of krypton atoms were analyzed by the time-of-flight spectrometer. Results indicated a clear quantum interference in the ionization signal versus the delay between the harmonic pulses. The experiment showed that high-resolution spectroscopy could be applied in the extreme ultraviolet using high-order laser harmonics.