Strong enhancement of electron-impact-ionization processes in hot dense plasma by transient spatial localization

Abstract

The current standard atomic collision theory cannot explain recent experiments on electron-ion collisional ionization processes in hot dense plasma. We suggest that the use of (distorted) plane waves for incident and scattered electrons is not adequate to describe dissipation during the ionization event. Random collisions with free electrons and ions in plasma cause electron matter waves to lose their phase, which results in partial decoherence of incident and scattered electrons. Such a plasma-induced transient spatial localization of the continuum-electron states significantly modifies the wave functions of continuum electrons, resulting in a strong enhancement of electron-ion collisional ionization of ions in plasma compared with isolated ions. We develop a theoretical formulation to calculate the differential and integral cross sections by incorporating the effects of plasma screening and transient spatial localization. The approach is then used to investigate electron-impact ionization of ions in solid-density magnesium plasma and gives results that are consistent with experiment. The correlation of continuum-electron energies is modified and the integral cross sections and rates increase considerably in hot dense plasma. For ionization of Mg9+ e+ 1s2 2s 2S → 1s2 1S + 2e, the ionization cross sections increase several-fold and the rates increase by one order of magnitude. Our findings shed new insight on collisional ionization and three-body recombination and should aid in investigations of the transport properties and nonequilibrium evolution of hot dense plasma.

The Strong Enhancement of Electron-Impact Ionization Processes in Dense Plasma by Transient Spatial Localization

“…The energy and momentum of the continuum electrons in dense plasma have a range of uncertainty because of the randomness of collisions and the resulting energy and momentum that is exchanged with other electrons and ions. As a result, the radial wave function of the continuum electrons (with central momentum ) is a superposition of the normalized wave function associated with energy within the uncertainty [ 24 , 69 ] where is the relativistic angular quantum number, A is a renormalization constant, and is the expansion coefficient of in momentum space. The normalized wave function is determined by solving the Dirac equation with the plasma screening potential and has a definite energy and momentum k .…”