Deep inelastic electron scattering on light nuclei

Czechoslovak Journal of Physics -     

Deep inelastic electron scattering from the deuteron

In the present lectures we discuss the role of nuclear structure effects in deep inelastic scattering of leptons on the deuteron. Also a problem of unfolding the neutron structure functions, spin-independent and spin-dependent, from the combined proton-deuteron data is considered.Lectures given (by the first author) at the Indian-Summer School on Electron Scattering of Nucleons and Nuclei, Prague (Czech Republic), September 1994.On leave from Bogoliubov's Laboratory of Physics, JINR, Dubna 141980, Russia.This work was supported in part by the Natural Sciences and Engineering Research Council of Canada. One of the author (LPK) wishes to thank NSERC for an international scientific exchange award that made it possible to visit the University of Alberta.     

Multiple inelastic electron scattering processes in thin molecular films: a simple model

Electron energy loss spectra of multilayer molecular films contain bands resulting from inelastic collisions at two or more sites within the film. The contributions of twofold loss processes are analysed for selected vibrational spectra of benzene and SF₆ using a simple model that was suggested previously and is extended here. It is shown that this analysis can be used not only to detect dipole scattering contributions to particular vibrational excitations. Combined with an estimate of the twofold loss spectrum based on the pattern of the fundamental bands the model also enables the identification of overtone and combination bands which is important for the detection of resonant processes.     

The energy dependence of the electron inelastic scattering mean-free-path in gold

The relative electron inelastic scattering mean-free-path in gold in the energy range 60–140 eV has been determined by the overlayer technique using synchrotron radiation photoemission spectroscopy from the 4f core levels of a tantalum foil substrate. The mean-free-path falls rapidly from 60 to 80 eV but is essentially constant from 100 to 140 eV.     

The influence of impurity formation on electron inelastic scattering of suspended graphene

This study reports on controlling the formation of nanoimpurities on suspended graphene to investigate the inelastic scattering of electrons using a two‐phonon Raman process. Results were analyzed by transmission electron microscopy (TEM) and scanning Raman spectroscopy in the same region of suspended graphene. The findings revealed that the area with a higher concentration of impurities shown in the TEM image corresponds directly to the area with a lower integrated intensity and a wider full width at half maximum in the Raman mapping of the 2D band and vice versa. The same trend is also apparent in the 2D′ and D + D″ bands. In conclusion, the results are explained by an increase in the electronic scattering rate due to impurities, which affects two‐phonon Raman scattering. Combining the TEM image and Raman mapping image effectively demonstrates how electron behavior is affected by the distribution of impurities in graphene systems. Copyright © 2012 John Wiley & Sons, Ltd.     

Creation of the resonanceΔ in inelastic electron scattering on nuclei

The creation of the resonanceΔ (1,232) in deep inelastic electron scattering on nuclei is studied. In the quasi-elastic process, the distortion of its wave function by an average potential is investigated. The same potential may lead to situations where the isobar is created in bound state orbits. The corresponding process is shown to contribute in the region of the dip in the cross sections. An experimental verification is suggested.     

The hydrogen hyperfine structure and inelastic electron proton scattering experiments

It is shown that present experiments on inelastic electron proton scattering can be used to set bounds to part of the proton polarizability contribution to the hyperfine structure of the ground state in the hydrogen atom.     

Transition probability functions for applications of inelastic electron scattering

In this work, the transition matrix elements for inelastic electron scattering are investigated which are the central quantity for interpreting experiments. The angular part is given by spherical harmonics. For the weighted radial wave function overlap, analytic expressions are derived in the Slater-type and the hydrogen-like orbital models. These expressions are shown to be composed of a finite sum of polynomials and elementary trigonometric functions. Hence, they are easy to use, require little computation time, and are significantly more accurate than commonly used approximations.     

Importance of longitudinal contributions to backward inelastic electron scattering

Coulomb contributions of multipolarity 2 are calculated for backward (θ = 180°) inelastic electron scattering by our improved DWBA code. General features are studied such as nuclear charge (Z) dependence, energy transfer dependence, momentum transfer dependence as well as the angle dependence near θ = 180°, with the help of a simple model for the transition charge density. We compare these features with PWBA and other simple approximations. We show, as a specific example, that the C2 contribution is comparable to the M1 and E2 multipole form factors for inelastic scattering to the rotational excited states of ¹⁸¹Ta.     

Further measurements of parity non-conservation in inelastic electron scattering

We have extended our earlier measurements of parity violating asymmetries in the inelastic scattering of longitudinally polarized electrons from deuterium to cover the range 0.15≤y≤0.36. The observed asymmetry shows only slight y dependence over this range. Our results are consistent with the expectations of the Weinberg-Salam model for a value of sin²θ_w= 0.224±0.020.     

Theory of adsorbate vibrational excitation by inelastic electron scattering

For electrons specularly reflected at a metal surface the differential cross-section for excitation of a single adsorbate vibration is calculated, with special application to the adsorbed CO group.     

First inelastic neutron scattering studies on thin free standing polymer films

Glass transition studies in free standing polymer films have revealed values of the transition temperature, T(g), which were substantially reduced below the bulk for sufficiently thin films. Here we report on the preparation of two stacks of free standing polystyrene films: 70 films with a thickness of h approximately 107 nm and 140 films with h approximately 55 nm with equivalent total sample thicknesses of approximately 7.5 microm. We have performed the first measurements on such samples using inelastic neutron scattering, and demonstrate that inelastic neutron scattering experiments, performed on the time-of-flight spectrometer IN6 and the backscattering spectrometer IN16 at the Institut Laue-Langevin, are feasible.     

First inelastic neutron scattering studies on thin free standing polymer films

Intermolecular coupling plays an important role in determining the dynamics and the mobility of polymeric and non-polymeric glass-formers. The breadth of the dispersion is an indicator of the intermolecular coupling strength. The coupling model relates intermolecular coupling through the breadth of the dispersion to the dynamics of bulk glass-formers. When a glass-former is confined in nanometer pores or in thin films and if there is absence of chemical and physical interactions with the wall, intermolecular coupling is reduced, resulting in an increase of mobility. The coupling model is used to account for such changes of relaxation time of 1) ortho-terphenyl and poly(dimethyl siloxane) confined in nanometer pores, 2) polymer thin film confined between two impenetrable walls from Monte Carlo simulation, and 3) polymer film confined by perfectly smooth and purely repulsive potential acting on the repeat units from molecular-dynamics simulation. The model continues to explain the opposite effects observed when there is an increase of intermolecular coupling due to the presence of chemical or physical interaction with the walls.Received: 1 January 2003, Published online: 8 October 2003PACS: 64.70.Pf Glass transitions - 68.60.Bs Mechanical and acoustical properties - 36.20.-r Macromolecules and polymer molecules     

Level shifts and inelastic electron scattering in dense plasmas

A completely quantum mechanical formalism has been developed to describe the high density plasma effects on fundamental atomic parameters. Both the bound and free electrons are treated by a method which in principle is similar to Hartree's self-consistent field method. The free plasma electrons' wavefunction is obtained from the Schrödinger equation with the effective pottential representing the spherically averaged Coulomb interaction with bound and free electrons. Results are given for level shifts, coefficients of transition probabilities, and electron collision cross sections of Ne⁺⁹ for temperatures of 200 and 500 eV for an electron density range of 1–6 × 10²⁴ cm^?3.