Multiphoton Ionization of Atoms

The alkali atoms are especially attractive for the investigation of multi-photon processes. The ionization potentials are small so that the energy of only a few visible photons is sufficient to ionize the atoms. Therefore, dye lasers can be used for the experiments and, in particular, make it possible to investigate, among other things, the wavelength dependence of the photoionization cross sections. On the other hand, the simplicity of the alkali energy level scheme is an advantage for the theoretical understanding and interpretation of the results.