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.

N -electron ground state energies of a quantum dot in magnetic field

Abstract: Using single-electron capacitance spectroscopy, we map the magnetic field dependence of the ground state energies of a single quantum dot containing from 0 to 50 electrons. The experimental spectra reproduce many features of a noninteracting electron model with an added fixed charging energy. However, in detailed observations deviations are apparent: Exchange induces a two-electron singlet-triplet transition, self-consistency of the confinement potential causes the dot to assume a quasi-two-dimensional character, and features develop which are suggestive of the fractional quantum Hall effect.

Identification of Reactive Species in Photoexcited Nanocrystalline TiO2 Films by Wide-Wavelength-Range (400−2500 nm) Transient Absorption Spectroscopy

Abstract: Reactive species, holes, and electrons in photoexcited nanocrystalline TiO2 films were studied by transient absorption spectroscopy in the wavelength range from 400 to 2500 nm. The electron spectrum was obtained through a hole-scavenging reaction under steady-state light irradiation. The spectrum can be analyzed by a superposition of the free-electron and trapped-electron spectra. By subtracting the electron spectrum from the transient absorption spectrum, the spectrum of trapped holes was obtained. As a result, three reactive speciestrapped holes and free and trapped electronswere identified in the transient absorption spectrum. The reactivity of these species was evaluated through transient absorption spectroscopy in the presence of hole- and electron-scavenger molecules. The spectra indicate that trapped holes and electrons are localized at the surface of the particles and free electrons are distributed in the bulk.

Microscopic processes in dielectrics under irradiation by subpicosecond laser pulses

Abstract: Transparent solids may show strong absorption when irradiated by a high-intensity laser pulse. Such laser induced breakdown is due to the formation of a free-electron gas. We investigate theoretically the role of ionization processes in a defect-free crystal, including in our model two competing processes: strong-electric-field ionization and electron impact ionization. Free-electron heating is described in terms of electron-phonon-photon collisions. Relaxation of the free electron gas occurs through electron-electron collisions and electron-phonon collisions. The latter are also responsible for energy transfer from the free-electron gas to the phonon gas. We solve numerically a system of time dependent Boltzmann equations, where each considered process is included by its corresponding collision integral. Our results show formation, excitation, and relaxation of the electron gas in the conduction band. We find that strong-electric-field ionization is mainly responsible for free-electron generation. No avalanche occurs at femtosecond laser irradiation. The electron density and the internal energies of the subsystems are calculated. Critical fluences obtained using various criteria for damage threshold are in good agreement with recent experiments.