Recoil-ion momentum spectroscopy

High-resolution recoil-ion momentum spectroscopy (RIMS) is a novel technique to determine the charge state and the complete final momentum vector P-R of a recoiling target ion emerging from an ionizing collision of an atom with any kind of radiation. It offers a unique combination of superior momentum resolution in all three spatial directions of Delta P-R = 0.07 all with a large detection solid angle of Delta Omega(R)/4 pi greater than or equal to 98%. Recently, low-energy electron analysers based on rigorously new concepts and reaching similar specifications were successfully integrated into RIM spectrometers yielding so-called 'reaction microscopes'. Exploiting these techniques, a large variety of atomic reactions for ion, electron, photon and antiproton impact have been explored in unprecedented detail and completeness. Among them kinematically complete experiments on electron capture, single and double ionization in ion-atom collisions at projectile energies between 5 keV and 1.4 GeV have been carried out. Double photoionization of He has been investigated at energies E-gamma close to the threshold (E-gamma = 80 eV) up to E-gamma = 58 keV. At E-gamma > 8 keV the contributions to double ionization after photoabsorption and Compton scattering were separated kinematically for the first time. These and many other results will be reviewed in this paper. In addition, the experimental technique is described in some detail and emphasis is given to envisaging the rich future potential of the method in various fields of atomic collision physics with atoms. molecules and clusters.