2007 Volume 76 Issue 2 Pages 133-140
We report on novel techniques used for measurement of an attosecond pulse train (APT) formed by the Fourier synthesis of high-order harmonic fields. Direct observation of the train feature of the APT revealed two kinds of autocorrelation signals, which are yielded via nonlinear interaction of the APT with an atom or a molecule, revealing the intrinsic characteristics of the APT.