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.

Self-trapping of electrons at the field-effect junction of a molecular crystal

Abstract: We consider the interface of a molecular crystal with a polar dielectrics. Coulomb interaction of free electrons in the molecular crystal with surface polar phonons of the dielectrics can lead to self-trapping of carriers. For typical parameters of molecular field-effect transistors the binding energy is found to be high enough to allow for the formation of a strongly coupled polaron. The effect is further enhanced in the presence of a bias electric field.

Influence of surface geometry on metal properties

Abstract: The influence of surface geometry on metal properties is studied within the limit of the quantum theory of free electrons. It is shown that a metal surface can be modified with patterned indents to increase the Fermi energy level inside the metal, leading to decrease in electron work function. This effect would exist in any quantum system comprising fermions inside a potential energy box. Also disclosed is a method for making nanostructured surfaces having perpendicular features with sharp edges.

Observation of dissociative quasi-free electron attachment to nucleoside via excited anion radical in solution.

Abstract: Damage to DNA via dissociative electron attachment has been well-studied in both the gas and condensed phases; however, understanding this process in bulk solution at a fundamental level is still a challenge. Here, we use a picosecond pulse of a high energy electron beam to generate electrons in liquid diethylene glycol and observe the electron attachment dynamics to ribothymidine at different stages of electron relaxation. Our transient spectroscopic results reveal that the quasi-free electron with energy near the conduction band effectively attaches to ribothymidine leading to a new absorbing species that is characterized in the UV-visible region. This species exhibits a nearly concentration-independent decay with a time constant of ~350 ps. From time-resolved studies under different conditions, combined with data analysis and theoretical calculations, we assign this intermediate to an excited anion radical that undergoes N1-C1′ glycosidic bond dissociation rather than relaxation to its ground state. Radiation-induced low-energy electrons in solution are implicated in DNA damage, but their relaxation dynamics are not well understood. Here the authors observe how quasi-free electrons dissociate glycosidic bonds via an excited nucleoside anion radical, whereas solvated electrons reside on the nucleoside as a relatively stable anion radical.

The Electrical Properties of Graphite

Abstract: The Hall coefficient and resistivity of a range of polycrystalline graphites with different crystal sizes and a single crystal of Travancore graphite have been measured over a wide range of temperature. The number of free electrons has been found to be approximately 6 $\times $ 10$^{18}$ per cm$^{3}$ at room temperature; the variation with temperature cannot be accurately determined. The deficit of electrons in poorly crystalline graphite gives rise to positive Hall coefficients. Quenching removes electrons, and a study of this process has enabled the ratio of the mobilities of positive holes and electrons to be estimated at 0$\cdot $80. An interesting effect has been observed in the variation of the Hall coefficient of the single crystal with field; no satisfactory explanation has been found for this phenomenon. The resistivity of polycrystalline graphite depends on the density and on the orientation and size of the crystals. From the variation of resistivity with temperature and the size of the crystals, the mean free path due to thermal scattering has been found to be 2350 angstrom at 273 degrees K; the variation of mean free path with temperature has been deduced. The product of effective mass and velocity of the free electrons has been determined as a function of temperature; the accuracy is limited by uncertainties in the number of free electrons.

The diffraction of electrons in gases

Abstract: The new wave mechanics has been eminently successful in correlating and accounting for the large amount of experimental data on the periodic properties of the atom. The applications of the new theory to aperiodic phenomena, though not nearly so numerous, have been attended with no less success; indeed, it is in these experiments on free electrons, in which diffraction patterns similar to those produced by beams of X-rays and light are obtained, that the wave nature of electrons is so clearly and objectively demonstrated. Such diffraction effects have been obtained by a number of investigators by scattering beams of homogeneous electrons in crystals, thin films and by a ruled grating. Similar effects are obtained when electrons are scattered by complex molecules, owing to the symmetrically situated nuclei in the molecular structure, and when α -particles are scattered by helium owing to interference between the waves of the scattered incident particles and recoiling helium nuclei.