Molecular imaging using recolliding electrons

When molecules are subject to intense laser pulses, electrons can be detached, accelerated and driven back to the molecule, resulting in electron–ion recollisions. Recolliding electrons probe the structure and dynamics of molecules. We review the theoretical concepts and experimental achievements towards using recollisions to image molecules. We classify these methods by the choice of the observed signal, which can be one of high-harmonic radiation, electrons from high-order above-threshold ionization, or fragment kinetic energies from recollision-induced dissociation or Coulomb explosion. It is shown that sub-Ångström and sub-femtosecond resolution is possible within these schemes.