Biomedical Engineering Reference
In-Depth Information
Chapter 7
A Multiple-Scattering Approach to Electron
Collisions with Small Molecular Clusters
Jimena D. Gorfinkiel and Stefano Caprasecca
Abstract
We present a method based on multiple-scattering to determine elastic
cross sections for electron collisions with molecular clusters. The method is based
on the calculation of accurate collisional information for the molecules constituting
the cluster that is then combined to obtain a cross section for interaction with the
whole system. The method provides a computationally cost-effective way of treating
low energy electron scattering from (homogeneous and heterogeneous) molecular
clusters and aggregates. Results for (H
2
O)
n
(n
2,5) and (HCOOH)
2
are presented;
the cross sections agree well with more accurate
ab initio
data.
D
7.1
Introduction
Clusters are aggregates of atoms or molecules with properties that are often between
that of a bulk and a gas but that, on occasions, are different from both. An extensive
literature is available on structural and electronic properties of clusters. In molecular
clusters, the interactions between sub-units (also called monomers) is limited to the
weak intermolecular forces: Van de Waals and dipole - dipole interaction, hydrogen
bonding, etc. [
1
].
Molecular clusters are models for solvation and are also important in atmospheric
processes. In the Earth's atmosphere, cosmic rays generate ions which then stabilise
by reacting with other atmospheric molecules and through charge-driven clustering
with polar molecules H
2
O, NH
3
[
2
,
3
]. Such clusters grow to form ultrafine aerosols
