Recoil Ion Momentum Spectroscopy Momentum Space Images of Atomic Reactions

Abstract

Recoil-ion momentum spectroscopy is a powerful tool for investigating the dynamics of ion, electron or photon impact reactions with atoms or molecules. It allows to measure the three-dimensional momentum vector of the ion from those reactions with high resolution and 4 π solid angle. In many cases already the recoil-ion momentum distribution alone unveils directly the physical processes dominating the reaction. The most detailed information, however is gained by combining the recoil-ion momentum measurement with the coincident detection of momentum vector of one or more emitted electrons or a measurement of the momentum exchange of the projectile. By such many particle momentum imaging one obtains a fully differential cross section of the reaction, i.e. for each registered event one measures the momenta of all particles and the full final state momentum space is covered in one experiment. Thus the experiment yields the square of the final state wave function of the reaction in momentum space. Such multidimensional data arrays can be sorted in many different ways after the actual experiment. Examples for ion impact ionization are discussed.