Probabilities of Radiative Transitions

In this chapter, we consider the probability of photoprocesses including bound–bound, bound–free, and free–free electronic transitions. This concerns atomic radiation transitions in the discrete energy spectrum, radiative recombination, Bremsstrahlung including polarization channel, photoionization, photodetachment of negative ions, and phase control of photoprocesses by ultrashort laser pulses. Considerable attention has been paid to various types of broadening of the spectral lines of atomic radiative transitions, including plasma broadening mechanisms. The rotational approximation of the Kramers electrodynamics is presented which is suitable for describing both free–free and free–bound electronic transitions in the high frequency limit. The photoionization of atoms is described both within the framework of a rigorous quantum mechanical approach and with the help of a number of approximate methods. Analytical generalized photoionization cross section formulas from K-, L-, M-, N-, and O-shell that include also possible inner-shell photoionization are presented. Finally, generalized scaled formulas for radiation recombination rates into all states with principal quantum numbers n = 1–9 and orbital quantum numbers l = 0–8 are given that can be applied for a large variety of practical cases.