RESONANT MULTI-PHOTON IONIZATION OF CESIUM ATOMS

The resonant multiphoton ionization (RMPI) phenomenon, in the case of caesium atoms interacting with the intense field of a neodymium-Glass laser is considered, presenting first a recount theory of RMPI, in a simplified form in order to obtain the main informations on the physics of RMPI. Then two experiments of RMPI are presented: four-photon ionization of the caesium atom in its ground state, with a three-photon resonance on the 6F level and three-photon ionization of the caesium atom is its 6**2P//3/////2 state with a two-photon resonance on the 12F level. In the first experiment, the internal structure of the resonant transition is resolved, enabling the authors to point out and analyze the important effect of pulse shapes and focusing conditions on the experimental results, which are discussed in detail. New interpretations of results published previously are also given. In the second experiment, the 12F fine structure was measured, showing that the limits imposed by the Doppler effect were reached. These experimental results are in good agreement with the theoretical predictions suggesting that the physical picture given of RMPI by recent works on this subject is satisfactory.