Multiphoton transitions to the continuum via multiple resonances
Farhad H. M. Faisal · Journal of Physics B Atomic and Molecular Physics · 1976
Multiphonon transitions to the continuum directly via multiple resonances and their mutual interactions are considered. The problem is treated quantum-electrodynamically by solving a system of (N levels+continuum) equations within the rotating-wave approximation. The transition rate per unit time exhibits strong intensity and frequency dependence. The mutual interactions of the resonances are found to generate 'cumulative frequency detunings' and 'cumulative power widths' which characterize and govern the transitions in the system. A four-photon transition via triple resonances is discussed in greater detail, and this shows inter alia variable 'power laws' that pass through several integer powers of intensity at specified conditions. The level shifts, which are found to arise naturally as integral parts of the transition process, are also given. The general result is presented.