Understanding energy loss in large-angle scattering of keV electrons from Ar and Ne

Abstract

We present measurements of the spectra of electrons with energy between 0.6 and 2.25 keV elastically and inelastically scattered from Ar and Ne over large angles (from 3 • to 135 • ). The intensity of the first loss feature [np → (n + 1)s], relative to that of the elastic peak, was determined and compared with the results of relativistic distorted-wave calculations (for the energy loss part) and a relativistic optical potential method (for the elastic peak). Good agreement was found. The distorted-wave calculations are compared with first Born calculations. At small angles, both theories coincide and estimates of the optical oscillator strength are obtained. However, at large angles, the first Born approximation predicts negligible intensity, in strong contrast to the distorted-wave theory and the experimental data. The implications of these results for the interpretation of measurements of the generalized oscillator strength are discussed.

Large-angle scattering of energetic electrons from Xe: A combined theoretical and experimental approach

“…In Ref. [4] we showed for Ne and Ar that calculations based on the distorted-wave framework give a reasonable description of the outermost excitations. Here we use the same theory for scattering from Xe but extend our comparison to deeper excitation energies below the continuum.…”

“…Both of these methods have recently been described (see Ref. [4], hereafter referred to as I) in connection with similar types of calculations in neon and argon. Consequently, only a brief description of these procedures, with particular regard to xenon, will be given here.…”

“…This theory was used before to describe the spectra of electrons scattered inelastically with energies between 0.3 and 2.5 keV from Ar and Ne [4]. For small scattering angles, this theory coincides with the first Born approximation (FBA), but at larger scattering angles its intensity exceeds that of the FBA by many orders of magnitude.…”

Dynamic behavior of valence-shell excitations of atomic neon studied by high-resolution inelastic x-ray scattering

“…The only available experimental data by high-energy electron impact at 2.5 keV is the state-resolved GOS measurements [9], to the best of our knowledge. As for the theoretical investigations, the GOSs or DCSs of the valence-shell excitations of neon were calculated by the FBA [35], the distorted-wave Born approximation [36], the frist-order many-body theory [37], as well as the relativistic distorted-wave Born approximation [38,39]. Recently, the RPAE method, in which the electronic correlation is carefully considered, was used to calculate the dynamic parameters of the valence-shell excitations of neon [12][13][14]17].…”

A high resolution and large solid angle x-ray Raman spectroscopy end-station at the Stanford Synchrotron Radiation Lightsource

“…Further on, the high energy resolution of the end station (∼ 270 meV at low-q) could also render the present end-station as a powerful tool to reveal new insights related to low-energy non-dipole transitions in atoms and molecular systems through q-dependent studies within the low-q regime. [50][51][52][53][54][55][56][57][58] Moreover, XRS from semicore levels of heavy elements studied with the present instrument will give improved resolution of the overlapping multiplet featuresan important improvement for broader application of XRS to f-electron systems. [59][60][61][62] The continuous progress with the x-ray optics as well as the availability of modern undulator radiation beamlines, such as the anticipated new undulator beamline at SSRL dedicated to high resolution x-ray spectroscopy, will further boost this technique to a wide range of applications.…”