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 H(2) 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 H(2)+, dephasing and rephasing of the vibrational wave packet that is formed in H(2)+ 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 H(2)+ (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 H(2)+ wave packet on field-dressed potential energy curves.