Comment on: An alternative approach for the determination of mean free paths of electron scattering in liquid water based on experimental data

TL;DR

This paper critically evaluates a recent simplified model for determining electron mean free paths in liquid water, highlighting issues with its methodology and questionable results, especially regarding comparisons with amorphous ice.

Contribution

The authors provide a detailed critique of the simplistic two-channel model and its application to experimental data, questioning its validity and the conclusions drawn.

Findings

Reported mean free paths are questionable.

The comparison with amorphous ice is invalid.

The simplified model has significant limitations.

Abstract

In a recent article, Schild et al. present what they call an alternative approach to the determination of mean free paths of electron scattering in liquid water. This by no means new approach is based on a very simplistic two channel model of electron scattering with only one fully elastic and one fully inelastic (total loss) channel. The parameterization consists of an elastic cross section, its angular dependence (DCS), and a cross section for electron loss by inelastic scattering. The two cross sections (or the equivalent MFPs) are determined from fits to experimental data (EALs and measured anisotropy parameters). The elastic DCS is calculated ab initio for various cluster models. Furthermore, they claim to find elastic and inelastic mean free paths that are much shorter than those for amorphous ice. We find that there are a number of issues both with the approach of the authors and with the comparison of their results with the literature. As outlined in the comment, the reported values for elastic and inelastic mean free paths are questionable and conclusions regarding the difference between electron scattering in liquid water and amorphous ice are invalid.