Molecular Dissociative Ionization and Wave-Packet Dynamics Studied Using Two-Color XUV and IR Pump-Probe Spectroscopy

We present a combined theoretical and experimental study of ultrafast wave-packet dynamics in the dissociative ionization of H₂ molecules as a result of irradiation with an extreme-ultraviolet (XUV) pulse followed by an infrared (IR) pulse. In experiments where the duration of both the XUV and IR pulses are shorter than the vibrational period of H₂;{+}, dephasing and rephasing of the vibrational wave packet that is formed in H₂;{+} upon ionization of the neutral molecule by the XUV pulse is observed. In experiments where the duration of the IR pulse exceeds the vibrational period of H₂;{+} (15 fs), a pronounced dependence of the H;{+} kinetic energy distribution on XUV-IR delay is observed that can be explained in terms of the adiabatic propagation of the H₂;{+} wave packet on field-dressed potential energy curves.