Imaging atomic scattering potential in centroidal diffraction of elastic electrons

Abstract

The Fraunhofer diffraction of quantum particles from materials with sharp electron-density edges or symmetric bond structures is ubiquitous. In contrast, diffraction from atoms with characteristic asymptotically-diffused electron distribution is far less intuitive, although known for many years. The current study unravels an unusual diffraction mechanism of elastic electrons from diffused atomic diffractors. Consequently, the fringe pattern converted to the Fourier reciprocal space maps out the effective scattering potential, which is not accessible in direct measurements. This may benefit benchmarking theory models, advances in atom-holography, plasma and astrophysical diagnostics, and accessing time-resolved potential landscapes. The study employs relativistic partial wave analysis with atoms modeled in the Dirac-Fock formalism and performs e-Cd measurements in absolute scale. Analysis for Mg, Ba, and Ra targets demonstrates the universality of the mechanism.

Figures (4)

• Figure 1: Absolute angular DCS of e-Cd for collision energies 3.4 (a), 6.4 (b), 10 (c), 15 (d), 20 (e), 40 (f), 60 (g), and 85 (h) eV are compared for current measurement versus calculation. The TCS comparison in Fig. S2 is given in SM SM_e-atomsc.
• Figure 2: FFT spectra of calculated DCS for collision energies in Fig. \ref{['fig1']}. Arrows point the peak locations.
• Figure 3: Diffractograms calculated for (a) e-Mg and (b) e-Cd.
• Figure 4: Effective potential $V_{\hbox{\scriptsize Eff}}$ [Eq. (\ref{['V_avg']})] averaged over the electron energies ($E_i$) in the range 0.1-100 eV using TCS with and without the resonance. The color bands correspond to $V(r,E_i)$. FFT peak locations, divided by two, for different collision energies are plotted by dots. For Cd (b), the dots are color-matched to respective curves in Fig. \ref{['fig2']}. Collision energies of some dots are indicated by horizontal lines and a few arrows.