Frequency-resolved autocorrelation measurement for characterization of an attoseconod pulse train

Abstract

We observed photoelectron spectra with two-photon ionizations of helium excited simultaneously by multiple-order harmonics. Correlation measurements, by utilizing these photoelectron spectra, between the two replicas of the harmonic pulse including the multiple-order harmonics exhibited the pulse envelopes with cross-correlations between the different order harmonics other than the autocorrelations. This type of correlation measurement is potentially applicable to fully characterize an attosecond pulse train by improving the resolutions of photoelectron spectra and of delay. © 2007 Springer-Verlag New York.