Electron impact ionisation cross-sections for complex molecules

The main goal of this work is to compute the total ionisation cross-section for electron scattering from various complex molecules. The targets chosen are pyridazine, alanine, glycine, benzoic acid, phenylacetylene, ethylbenzene and n-propylbenzene. There is no previous literature available for these molecules except for pyridazine, alanine and glycine, and hence we present the first report of their ionisation cross-section. We apply the complex scattering potential-ionisation contribution (CSP-ic) method to compute the cross-sections from the respective ionisation threshold to 5000 eV. The result for the pyridazine molecule shows an excellent agreement with the available experimental data and binary encounter-Bethe (BEB) cross-sections. In the absence of any experimental comparison for other molecules, we have also calculated their BEB ionisation cross-sections. These two methods are well known for giving reasonable estimates of the ionisation cross-sections. The CSP-ic method is based on the molecular structure and properties, while the BEB method deals with molecular orbitals. Thus, comparing the two results will check the accuracy of these theoretical models and further increase the credibility of the reported cross-section. In general, fairly good agreement is observed between the two results. However, any inconsistencies observed are backed by valid reasons. (paper)