Analysis of low-energy electron scattering cross sections via effective-range theory

Abstract

An investigation of several alternative representations of modified effective-range theory (MERT) has been carried out for low-energy electron scattering from the rare gases argon, neon and krypton in an effort to determine the energy range over which they can be applied to the analysis of scattering cross sections. One purpose of the MERT analysis is to provide a bridge from a total cross section to a momentum transfer cross section in order to compare the results of beam experiments with those of electron swarm experiments. Simulations using published (theoretical) phaseshifts indicate that extended versions of the standard effective-range theory with five adjustable parameters are required to give an adequate description of the phaseshifts for argon. A five-parameter MERT fit gives a good representation of a recent e--Ar total cross section experiment at energies less than 1.0 eV. The resulting momentum transfer cross section is in agreement with a momentum transfer cross section obtained from a swarm experiment at energies below 0.3 eV, but at energies greater than 0.5 eV there are differences of up to 20%. The application of MERT to neon and krypton total cross section data has also been investigated. The derivation of momentum transfer cross sections (via MERT) for both these atoms involves much larger uncertainties than was the case for argon.