MULTIPLE-PHOTON VERSUS MULTI-PHOTON ABSORPTION IN THE THEORY OF RESONANT IONIZATION

The author has identified his result for resonant ionization by the simultaneous absorption of two photons by a ground-state electron [Phys. Rev. A 17, 659 (1978)] with the high-laser-power large-intermediate-state ionization rate result derived by Eberly and co-workers using a steady-state rate theory. This result gives R22 for all power levels considered, where R is the one-photon ionization rate for the intermediate state and 22 is its steady-state population factor. The result can be cast in this form, but it is found that 22 must be much less than 11, the ground-state population factor. Thus the resonant process can be described by a rate limit for conserving energy by simultaneous absorption only when the ground-state population factor remains unity to order 2R2, where is the Rabi rate for the bound-bound transition. In other words, the simultaneous and sequential processes are physically equivalent in this limit. © 1979 The American Physical Society.