Performance of binary‐encounter‐Bethe (BEB) theory for electron‐impact ionization cross sections of molecules containing heavy elements (Z > 10)

Abstract

The binary-encounter-Bethe (BEB) theory developed by Kim and coworkers has been successful for computing electron-impact ionization cross sections of many molecules. However, some recent publications have stated that BEB theory performs poorly for molecules that contain heavier elements such as chlorine and sulfur. We have found that the BEB calculations in those publications were performed incorrectly. When performed correctly, BEB predictions are as good for heavy-element molecules as for light-element molecules. We recommended recently that an alternative, less-confusing procedure be used for molecules that contain heavier elements. The alternative procedure, based upon effective core potentials (ECPs), does not require explicit kinetic energy corrections. For peak cross sections of a group of 18 molecules, the root-mean-square difference between BEB predictions and experimental values is 13%. Results

Electron impact ionisation cross sections of cis- and trans-diamminedichloridoplatinum(II) and its hydrolysis products

“…This facilitates the quantum chemical calculations and allows, to some extent, the incorporation of relativistic effects stemming from inner electrons with high kinetic energy. Due to the lack of inner radial nodes of the pseudo-valence orbitals, their kinetic energies are lower than normal and Equation (3) can be used to determine the BEB cross section [32]. Using the BEB method in conjunction with ECPs has earlier been recommended over the use of all-electron basis sets for molecules that contain heavy (with atomic number Z > 10) atoms [33].…”

Electron impact ionisation cross sections of iron oxides

“…This facilitates the quantum chemical calculations and allows the incorporation of relativistic effects. Due to the lack of inner radial nodes of the pseudo-valence orbitals, their kinetic energies are lower than normal and equation (3) can be used to determine the BEB cross section [50] avoiding the requirement of introducing an additional modification in equation (3) which became known as "acceleration correction" [51]. This combination of methods has earlier been recommended over using all-electron calculations for molecules that contain heavy atoms (with atomic number Z > 10) [52].…”

Electron impact ionisation cross sections of iron hydrogen clusters

“…This facilitates the quantum chemical calculations and allows the incorporation of relativistic effects. Due to the lack of inner radial nodes of the pseudo-valence orbitals, their kinetic energies are lower than normal and equation (3) can be used to determine the BEB cross section [46]. In this work we compare all-electron and valence-only methods to obtain BEB cross sections.…”