Tracking the nuclear-wave-packet dynamics on excited bound states of Ar2+ in strong laser fields

We experimentally investigated the photoionization and fragmentation of a van der Waals cluster of argon dimer (Ar2) exposed to intense laser fields. By performing femtosecond pump-probe experiments in a reaction microscope, we tracked the spatiotemporal evolution of the nuclear wave packet (NWP) launching onto the excited bound states of Ar2+. By interrogating the measured time-resolved vibrational structures in the kinetic energy spectra obtained from Coulomb explosion imaging of the Ar2+ NWP, the vibrational revival and rotational excitation of the long-living rovibrational NWP were observed in real time. The vibrational populations of the NWP on the potential curves of three excited bound states of Ar2+, i.e., I(3/2)g, II(1/2)u, and I(3/2)u, were identified by the Fourier analysis of the time-dependent kinetic energy spectra of nuclear fragments.