Observation of inner electron ionization from radial rydberg wave packets in two-electron atoms

Generalized n-photon resonant 2n-wave mixing in an (n+1)-level system with phase-conjugate geometry

A generalized scheme for phase-conjugate resonant 2n-wave mixing, which has a high efficiency and is easy for phase matching, is proposed. As a new type of coherent laser spectroscopy this approach can be employed for studying highly excited atomic states or states with a high angular momentum. To demonstrate its feasibility we have studied the doubly excited autoionizing Rydberg states of Ba by phase-conjugate six-wave mixing, and have furthermore achieved eight-wave mixing in Na. This method may find wide application in related areas such as coherent transient spectroscopy, Autler-Townes spectroscopy and electromagnetically induced transparency. In particular, it may provide new insights into the nature of highly excited states.

Time-domain investigation of electron recapture via post-collision interaction in a double photoionization continuum

Picosecond laser pulses have been used to sequentially photoionize both valence electrons from neutral Ba atoms, producing two radially localized continuum wave packets. The Coulomb interaction between the two outgoing electrons can result in the recapture of one of the electrons by the parent ion. The energy distribution of Rydberg ions formed via this "post-collision" interaction is measured as a function of the delay between the ionizing laser pulses. The experimental data are in agreement with the results of both a quantum sudden approximation and a classical simulation.