Lumped-state CRE Modeling of the Ionization Dynamics of O- and N-like Krypton

An often used approximation employed to simplify the problem of modeling the L- and M-shell ionization dynamics of moderate to high atomic number plasmas is to lump the states within each $n\ell$ multiplet of each ionization stage, and historically, this approximation has been applied assuming the multiplet substates are in LTE with respect to one another. In both Fe and W Z-pinch plasmas, this assumption has been shown to break down in ionization stages where the ground state has no multiplet structure \footnote{K. G. Whitney, et. al., J. Phys. B, \bf{40}, 2747 (2007).}. In this talk, we study the subpopulation dynamics in O- and N-like ionization stages where significant amounts of population can be stored in excited states and where ground states have multiplet structure. The non-LTE behavior of the following states is calculated: the ground states, the $\Delta n=0$, and the $2p^33\ell$ or $2p^23\ell$ excited states of O-like and N-like Kr respectively, and used to determine the impact on lumped state excitation and ionization rates and on the MHD of Z-pinch Kr implosions. In particular, the reduction of the Einstein decay rates of the $n=3$ states as a function of ion density is calculated.