Laser Spectroscopy of Negative Ion Beams

The availability of intense tunable and fixed frequency lasers has made it possible to investigate photon-ion interactions in crossed beam experiments. The short wavelength limitations of current lasers result in the greatest variety of applications having been made to studies of photon interactions with negative ions. Two major experimental approaches have been developed: fixed frequency laser negative ion photoelectron spectroscopy and tunable laser photode-tachment/photodissociation spectroscopy. The former approach is best suited for determination of electron affinities and structural properties of ions and free radicals, while the latter method provides highly accurate electron affinities and dynamical information on electron-molecule interactions. It is also possible to determine the internal energy content of negative ions. The experimental techniques and their limitations will be discussed in the form of several case studies: OH , C2 and the transition metals. Finally an attempt will be made to ascertain promising avenues for new investigations in this field.