Investigation of Population Inversion in Dense Recombining Plasmas.

The dynamics of the population density for the n-th atomic state of ions within a uniform, stationary, rapidly cooling plasma are expressed in terms of a set of coupled differential equations and solved numerically by standard techniques thus yielding a time description of the ion population levels. An emphasis is placed upon the prediction of population inversion in dense recombining plasmas. Electron collisional interactions are given in terms of a set of analytic, semi-empirical cross sections for which improved numerical approximations are utilized for the first time. A graphical format of the relationship of the total plasma electron temperature drop as a function of the temperature decay time in the prediction of population inversion is displayed. In addition, a set of iterative analytic approximations to the time description of the population densities for the case of instantaneously cooled collision dominated plasmas are given.