Reconsidering the numerous conceptions as they have been developed in atomic physics (self-consistent field), heat and charge transport theory (carrier-enhanced and radiation-induced conductivity) and many other related fields for iteratively solving the corresponding integro-differential equation systems we come now to propose a new approach to the subject addressed in the title. This method has been implemented in a FORTRAN code, allowing for a self-consistent solution of kinetic equations on a quite broad scale. However, in treating a particular problem (irradiated semiconductor, ionisation gas detectoed etc.) it appears recommendable to employ a confined specialized version. Model calculations of a (a.c. or d.c. driven) gas ionisation chamber have been carried out to demonstrate the systematizing potential of the present approach.