Free electron model

About: Free electron model is a research topic. Over the lifetime, 4678 publications have been published within this topic receiving 103535 citations.

Effects of free electrons and quantum confinement in ultrathin ZnO films: a comparison between undoped and Al-doped ZnO.

Abstract: Band gaps and exciton binding energies of undoped and Al-doped ZnO thin films were determined from optical absorption measurement based on the Elliott’s exciton absorption theory. As compared to the undoped films, the doped films exhibit a band gap expansion and a reduction in the exciton binding energies due to the free electron screening effect, which suppresses the excitonic absorption and results in a blue shift of the absorption edge. The undoped and doped films show the same quantum size dependence, i.e. both the exciton binding energies and band gap energies increase with decreasing grain size of the oxides.

A global model for the afterglow of pure argon and of argon with negatively charged dust particles

Abstract: Zero-dimensional, space-averaged global models of argon dust-free and dusty afterglow plasmas are developed, which describe the time behaviour of electron ne(t) and Ar ∗ metastable nm(t) densities. The theoretical description is based on the assumption that the free electron density is smaller than the dust charge density. In pure argon, fairly good agreement with the experimentally measured densities and their decay times in the afterglow is obtained when the electron energy loss term to the chamber walls is included in the electron energy balance equation. In dusty plasma afterglow, the agreement between theory and experiment is less satisfactory. The calculated metastable density is 3 times smaller than the measured one and the electron decay is much faster in the late afterglows. The difference should probably arise from the assumption that the electron energy distribution function is Maxwellian. Different sources of secondary electrons in the dusty plasma afterglow are analysed. Comparison of the model with experimental results of argon dusty plasma suggests that the metastable pooling could be the source of the experimentally observed electron density increase in the early afterglow but electron generation from metastable–dust interactions cannot be fully discarded. (Some figures in this article are in colour only in the electronic version)

Transient interference implications on the subpicosecond laser damage of multidielectrics

Abstract: Laser-induced damage in optical thin films with subpicosecond pulses is investigated. A model dedicated to optical interference coatings and based on the rate equation for free electron generation is introduced. It takes into account the transient interference effects induced by changes in the dielectric function during the laser pulse and its feedback effect on the electron density distribution in the multilayer stack. Simulations are compared to experiments on HfO2 and Ta2O5 films with pulses ranging from 45 fs to 1 ps. It is shown that this approach can improve the interpretation of femtosecond and picosecond laser induced damage in thin films.

Ion gyroradius effects on particle trapping in kinetic Alfvén waves along auroral field lines

Abstract: In this study, a 2D self-consistent hybrid gyrofluid-kinetic electron model is used to investigate Alfven wave propagation along dipolar magnetic field lines for a range of ion to electron temperature ratios The focus of the investigation is on understanding the role of these effects on electron trapping in kinetic Alfven waves sourced in the plasma sheet and the role of this trapping in contributing to the overall electron energization at the ionosphere This work also builds on our previous effort [Damiano et al, 2015] by considering a similar system in the limit of fixed initial parallel current, rather than fixed initial perpendicular electric field It is found that the effects of particle trapping are strongest in the cold ion limit and the kinetic Alfven wave is able to carry trapped electrons a large distance along the field line yielding a relatively large net energization of the trapped electron population as the phase speed of the wave is increased However, as the ion temperature is increased, the ability of the kinetic Alfven wave to carry and energize trapped electrons is reduced by more significant wave energy dispersion perpendicular to the ambient magnetic field which reduces the amplitude of the wave This reduction of wave amplitude in-turn reduces both the parallel current and the extent of the high energy tails evident in the energized electron populations at the ionospheric boundary (which may serve to explain the limited extent of the broadband electron energization seen in observations) Even in the cold ion limit, trapping effects in kinetic Alfven waves lead to only modest electron energization for the parameters considered (on the order of tens of eV) and the primary energization of electrons to keV levels coincides with the arrival of the wave at the ionospheric boundary