Effective statistical weights of bound states in plasmas

Abstract

Abstract. Based on recent advances in the study of the statistics of interparticle distances and angles in plasmas, we develop an approach for the determination of the effective statistical weights of atomic (ionic) quantum states in ideal and nonideal plasmas. This approach allows one to account naturally for the effects of both the perturbation of the bound states by the neighboring ions and for the binding energy reduction due to the screening of the Coulomb interaction. We analyze the roles of tunneling and overbarrier escape of the optical electron from the parent ion potential well. The effects of neighbor ions and free electrons on these processes, and the simultaneous presence of several perturber ion species in the plasma are treated. We show that the present approach offers significantly more accurate effective-statistical-weight values in comparison to the existing theoretical treatments, and yields physical expressions for the empirical factors of the existing theories. Examples of calculations of effective statistical weights are given. The effects of the atomic (ionic) states collectivization on the collisional-radiative kinetics of dense plasmas are discussed.

Progress in line-shape modeling of K-shell transitions in warm dense titanium plasmas

“…The corresponding states with a vacancy in either K or L shell (e.g., 1s2s 2 2p 6 3s 2 3p 5 4s and 1s 2 2s 2 2p 5 3s 2 3p 5 4s) were excluded from the calculations as well. It should be noted that the energies of some of the 4s-excited states are only slightly higher than the ionization threshold, therefore a more scrupulous approach would be to treat such states within the effective-statistical-weights model [16,17], which is similar in spirit to using the Planck-Larkin renormalization of the partition function, as is done in [9]. However, the contribution of the 4s states to the lineshapes turned out to be very small.…”

Classical molecular dynamics simulations of hydrogen plasmas and development of an analytical statistical model for computational validity assessment

“…Moreover, it is seen that the average potential energy of free electrons lies slightly below zero. This plasma collective effect naturally emerges from the simulation and reflects the fact that many electrons in the plasma have a negative total energy and are not bound to a particular positive ion but to the plasma as a whole, hence they sometimes are referred to as collectivized electrons [57][58][59]. This behavior has to do with the effect of ionization potential depression (IPD) [57,60] that appears in dense plasmas and also illustrates how diverse the information provided by MD simulations can be.…”

“…This plasma collective effect naturally emerges from the simulation and reflects the fact that many electrons in the plasma have a negative total energy and are not bound to a particular positive ion but to the plasma as a whole, hence they sometimes are referred to as collectivized electrons [57][58][59]. This behavior has to do with the effect of ionization potential depression (IPD) [57,60] that appears in dense plasmas and also illustrates how diverse the information provided by MD simulations can be. In fact, some IPD investigations in aluminum plasmas at and out of thermodynamic equilibrium have already been performed by using multicomponent classical MD simulations [61,62].…”

Physical Models of Plasma Microfield

“…This effect leads to the finite number of really existing excited states and ensures the convergence of statistical sums. The other physical consequence is the lowering of ionization potential, which influences on relation of equilibrium concentrations of atoms and ions, and thereby on the degree of plasma ionization [146,[148][149][150][151][152][153][154][155][156][157][158][159]. These tendencies both are visualized in observations by decreasing of spectral line intensities, originating from the upper levels to the extent of advancing to the continuum.…”