Variation of the mechanism of Ba/sup 2+/ ions formation during multiphoton ionisation of atoms

Summary form only given. Beginning with first experiments, where the effect of doubly-charged ions formation was discovered, intensive investigations to determine the mechanism leading to the production of doubly-charged ions in different spectral ranges are carried out. The main goal of our work is the creation of conditions for realization of direct two-electron mechanism of Ba/sup 2+/ ions formation in the visible spectral range. The experimental setup consists in following: during ionization of Ba atoms by visible laser radiation we realized strong additional perturbation of atoms by laser radiation of another frequency range.