The generation and detection of Rydberg electron wavepackets using picosecond lasers is discussed with reference to the observation of the dynamics of spin–orbit autoionization in Xe. A multiphoton (nanosecond + picosecond) excitation scheme is employed with two–photon phase–sensitive detection, based on the observation of Ramsey interference fringes. To complement the experiment, time–dependent multichannel quantum–defect theory (TD–MQDT) calculations have been developed to investigate the dynamics of a spin–orbit autoionizing Rydberg wavepacket in Ar. The time–dependent partial photoionization cross–sections reveal interesting interference patterns in the recurrence spectra which are accounted for in terms of the quantum defects of the autoionizing channels. Finally, the rovibrational and rotational autoionization dynamics of a Rydberg wavepacket in H2 are investigated using TD–MQDT. It is demonstrated that, in the time–domain, the configuration interaction between rotational channels can be described quantitatively in terms of an interaction time. In contrast to the rovibrational autoionization lifetime, which is determined by the classical orbit period (∞n3, the rotational autoionization lifetime is determined by the kinetic energy of the electron wavepacket following collision with the ion core.