Multiphoton Ionization

G. A. Delone, Nikolai B. Delone

S. L. Chin, P. Lambropoulos

Y. Teraoka, Yuuki Sato, J. Murakami

Multiphoton ionization (MPI) via two-photon resonance with high-lying Rydberg levels is observed on Na and K atoms in modest (12--120 V/cm) dc electric fields. The field-induced MPI signals are manifested to such an extent that the nominally forbidden MPI via two-photon resonance with the np levels is induced at the same signal levels as or more intensely than the allowed MPI via the ns and nd Rydberg levels. The intensity inversion between the allowed and the forbidden MPI signals is observed on the K atoms in the wavelength region where the two-photon energy is very close to the field-ionization limit.

P. N. Lebedev

Nikolai B. Delone

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.

Douglas Jackson, James J. Wynne, Peter H. Kes

A general theoretical model for the treatment of multiphoton ionization is presented. In this treatment, we have explicitly included coherent effects resulting from harmonic generation. The predictions of this model are in agreement with experimental observations that we present in this paper. In addition, the model is contrasted with much earlier theoretical treatments of multiphoton ionization and accounts for the anomalous multiphoton-ionization behavior reported by others in the literature.