We report here the measurement of the resonance spectrum of different highly\|excited states of Yb atom by means of multiphoton excitation in the applied electric field from near zero to 15000V/cm.The investigated resonance peaks are identified and the selection rules and the intensities of the transition lines are discussed.The evolutions of the lines in applied electric fields are observed and analyzed.The results show directly that transitions involving the excitation of the 4f\+\{14\} subshell play an important role in the spectral behaviour of highly\|excited states of Yb atom.
The most important results of study of multiphoton ionization of atoms are reviewed. Discussions are presented of specific features of the process, theoretical methods of description of ionization of atoms in a strong light field, the basic principles of design of experiments in which intense laser radiation is used, results of investigation of direct and resonance processes of multiphoton ionization, and the mutual relation between multiphoton processes (multiphoton excitation and ionization) and various phenomena leading to perturbation of the spectrum of bound states of an electron in an atom under the influence of a strong light field.