Validation of theoretical approaches for elastic electron scattering cross sections of polyatomic molecules based on experimental data of propane

Propane is an important filling gas in tissue-equivalent radiation detectors. After measuring the doubly differential ionization cross sections, the differential elastic electron scattering cross sections of propane were, to a large extent, completely determined both experimentally and theoretically. In this context, two well-known theoretical approaches were evaluated on the basis of experimental data.

Electron scattering cross sections of organic molecules are important data for various scientific fields of application. As experimental data for these cross sections are only available for a limited number of molecules and for restricted energy and angular ranges, semi-empirical or theoretical models are frequently used to determine cross sections. After evaluating a semi-empirical model for the doubly differential ionization cross sections [1], the accuracy of two theoretical approaches for differential elastic electron scattering cross sections  of polyatomic molecules was investigated based on the experimental data of propane.

Using the IAM-SCAR method [2] and the modified-independent-atom model (MIAM) [3], differential elastic electron scattering cross sections of propane as a function of the scattering angle were calculated and compared with experimental data for electron energies between 20 eV and 1 keV. Figure 1 shows the comparison for two selected energies.

Fig. 1:   Differential elastic electron scattering cross sections  of propane as a function of the scattering angle for primary energies of 60 eV (a) and 200 eV (b). The symbol (¡) represents the experimental data. The solid and dashed lines each represent the results calculated using the MIAM [3] and the IAM-SCAR method [2].

The calculations revealed that the IAM-SCAR method – which is used the most frequently because of its simplicity – only roughly reflects the measurement data for the energy range that was investigated. However, MIAM – which considers multiple scattering within a molecule – was able to attain a considerably better agreement for electron energies above 40 eV with the measurement data.

Literature

[1]    W. Y. Baek, M. U. Bug, H. Nettelbeck, and H. Rabus, Eur. Phys. J. D 73, 61 (2019)

[2]    F. Blanco and G. García, Phys. Lett. A 330, 230 (2004)

[3]    S. Hayashi and K. Kuchitsu, J. Phys. Soc. Jpn 41, 1724 (1976)