Inelastic Interactions Of Electrons Research Articles

An approach to reflection electron energy loss spectroscopy of overlayer systems

The high surface sensitivity of Reflection Electron Energy Loss Spectroscopy (REELS) should be helpful in the characterization of systems consisting of a few monolayers on a substrate. To unravel the dependence both on the material and layer thickness a simple model of the signal formation in REELS is used which requires probabilities of different elastic and inelastic electron interactions with single atomic layers. Their estimation from experimental and theoretical results is described and discussed. The relative signal intensities are given for different systems as a function of the number of monolayers. These curves show a maximum with overlayer thickness if the probability of elastic backscattering of the substrate is higher than that of the overlayer.

A model of processes determining the intensity of DAPS and AEAPS signals

A simple model including different processes important for the creation of APS signals formed by electrons is proposed. Mean probabilities of elastic and inelastic interactions of electrons with individual atom layers in the solid are introduced. The contribution of different layers to the DAPS and AEPS signals and the dependence of these signals on the interaction parameters are calculated.

Nonlinear resonant interaction between acoustic impulse and electrons in superconductors

The problem of inelastic electron interaction in a perfectly pure superconductor with a longitudinal sound impulse is considered. It is shown that the problem reduces to the equivalent one of elastic scattering by the static potential, and the sound absorption is expressed in terms of the reflection coefficient of this scattering. The classical and quantum properties of the scattering are studied and the phase region in which new excitations are created is indicated. A formula is derived that expresses the density matrix of the excitations created in terms of the exact scattering matrix of an impulse. The quasiclassical creation of excitations by a smooth-shaped impulse is investigated with regard to both overbarrier and underbarrier processes.

Relative intensities in X-ray photoelectron spectra. Part IX. Estimates for photoelectron mean free paths taking into account elastic collisions in a solid

By means of the Monte Carlo method the angular dependences of photoelectron peak intensities have been calculated for substrates covered with films of various thicknesses D. The calculations have been carried out for several sets of parameters of the elastic and inelastic interactions of electrons with solids and for various experimental geometries. On the basis of numerical theoretical results, analytical expressions are derived for estimating the difference between the effective mean free path of photoelectrons (λ eff) and the inelastic mean free path (λ n) in solids. These expressions are used to analyse experimental data for the determination of thin-film thicknesses by means of ESCA. It is concluded that the values determined experimentally are apparently D/λ eff ratios — not D/λ n, as is usually assumed. The importance of the results obtained is discussed with reference to the determination of photoelectron mean free paths in solids and of thin-film thicknesses by means of ESCA.

Straggling of Energy Loss for Electrons Transmitted through Aluminum

A study of the energy loss spectra of electrons transmitted through aluminum foil was carried out. Inelastic interactions of electrons with the conduction band as well as inner shells of aluminum have been considered. Energy loss spectra were computed for several monoenergetic electron sources and film thicknesses. Theoretical results have been compared with available experimental data.

Straggling and plasmon excitation in the energy loss spectra of electrons transmitted through carbon

A model is described for the calculation of differential inverse mean free paths (DIMFPs) for the inelastic interactions of electrons with solids. The energy loss function Im{-1/ ε( q, ω)} is represented as a sum of Drude-type functions. The adjustable parameters in the energy loss function are fixed by a fit to the energy loss function in the optical limit ( q → 0) obtained from data on the optical constants of glassy carbon. The extension of the optical energy loss function to arbitrary values of q in this model leads to an analytical expression for the DIMFP. Energy loss spectra for low energy electrons (less than 2000 eV) transmitted through carbon foils of various thicknesses are determined by solving the transport equation using a convolution method and the DIMFPs determined as described above. Comparisons of these calculated spectra with those measured by Jacobi show that the model provides a good description of both the broad straggling distribution and the fine structure due to plasmon excitation.

Inelastic Interactions of Electrons with Polystyrene: Calculations of Mean Free Paths, Stopping Powers, and CSDA Ranges

A theoretical description of the inelastic interactions of electrons with solid polystyrene is presented. The response of the valence electrons to energy and momentum transfers is determined by a model insulator theory; carbon K-shell ionization cross sections are derived from atomic, generalized oscillator strengths. Contributions to the inverse mean free path and stopping power due to these two excitation processes are derived and tabulated for incident electrons with energies from 10 eV to 10 keV. Electron ranges in the continuous-slowing-down approximation are calculated and tabulated for electrons with energies from 15 eV to 10 keV.

Quantum Scattering Approach to Auger Neutralization of Ions by Metals

This paper discusses in some detail the application of quantum scattering theory to the problem of Auger neutralization of ions at a solid surface. The formalism for rearrangement collisions in the distorted wave Born approximation has been used to calculate the secondary electron distribution and the total yield for the case of He+ on W. The distortion of the ion and atom motion by the solid is shown to play an important role in the neutralization process. This effect accounts for the observed broadening and shift in the secondary electron energy distribution. Additional points discussed include effects of inelastic projectile scattering, changes of the energy levels in the system during the neutralization process, and the probable effect of inelastic electron interactions.