Imaging of valence shell dynamics using intense laser pulses

Electron correlation is one of the main frontiers of modern science and of fundamental importance to such diverse fields as, e.g., many body systems, superconductivity and quantum computing. At the ultrafast laser frontier electron correlation has found prominence in the dramatic enhancement of multiple ionization and high harmonic generation. The underlying mechanism, called recollision, forms the foundation of attosecond science. However, above a certain threshold intensity the laser field-electron coupling dominates electron correlation and recollision is no longer important. Hence, electron correlation was assumed to be restricted to lower laser intensities. Only recently experimental evidence has corroborated the notion that the creation of a continuum electron wave packet by laser pulses often entails a correlated electronic hole wave packet in the ion in particular at those higher laser intensities.