Total Cross Sections for Electron and Positron Scattering on Molecules: In Search of the Dispersion Relation

Abstract

More than one hundred years of experimental and theoretical investigations of electron scattering in gases delivered cross-sections in a wide energy range, from few meV to keV. An analogy in optics, characterizing different materials, comes under the name of the dispersion relation, i.e., of the dependence of the refraction index on the light wavelength. The dispersion relation for electron (and positron) scattering was hypothesized in the 1970s, but without clear results. Here, we review experimental, theoretical, and semi-empirical cross-sections for N2, CO2, CH4, and CF4 in search of any hint for such a relation—unfortunately, without satisfactory conclusions.

“Atoms” Special Issue (Electron Scattering in Gases—From Cross Sections to Plasma Modeling)

“…The volume concludes with our contribution [16] that proposes the re-opening of the discussion on some possible "invariance" parameters in electron and positron scattering. All the contributions of this volume relate total and partial cross sections to other atomic/molecular parameters.…”

“…In this volume, we present a "cross-section" of different approaches, applications and processes, from industrial plasmas [3,4] to molecules of biological interest [5][6][7]; from experiments at ultra-low temperatures [8,9] to processes relevant for thermonuclear synthesis [10]. Thanks to a global response to the invitation, this volume hosts in an equilibrated manner the experimental aspects [6,8,9], ab-initio theories [7,[10][11][12] and semi-empirical approaches [13][14][15][16], both for electron and positron scattering [11,[15][16][17].…”