Abstract
We observed the ultrafast dynamic evolution of vibrational wave packets generated in the ground
electronic state of a D2
+/H2
+ ion using a pair of attosecond pulse trains (APTs), formed with the high-
(7th-order and higher) and low- (5th-order and lower) order harmonic fields of a sub-15 fs Ti:sapphire
laser pulse. The kinetic energy release spectrum of the fragment ions of D+/H+ exhibited a twodimensional
spectrogram of the wave packet by scanning the delay between the two APTs in the pair.
Due to the simplicity of the one-photon excitation for the fragmentation in the probe process, we
developed a novel method by mimicking the frequency-resolved optical gating technique to retrieve the
complex wave packet amplitudes at ionization. The retrieved amplitude exhibited a nontrivial phase
modulation, which can be interpreted as a ~1 fs settling time of the vibrational wave packet at ionization.
