For multiphoton processes, the higher-order terms of the perturbation series are treated by summing the class of irreducible diagrams. This allows the examination of the behavior of the cross section as a function of the incident photon flux at arbitrarily large intensities by means of analytic continuation to the nonperturbative region. The case of four-photon ionization of the ground state of hydrogen is discussed as an example.
No takes yet. Share an insight, caveat, or question.
Gontier et al. (1975) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: