Measuring ionization cross sections by electron impact

P. PÉREZ; A. SEPÚLVEDA; CASTELLANO, G.; J. TRINCAVELLI

Córdoba

Congreso; International Symposium on Radiation Phsics - 14; 2018

International Radiation Phsics Society

The thin-target method is often used to experimentally determine ionization cross sections, as the involved formalism is very simple. However, several experimental complications arise in the preparation of thin films and in the implications of the low counting statistics in the results. Alternatively, thick-target methods provide higher counting rates, but several approaches must be faced in order to achieve the searched cross sections. In this work, the integro-differential approach is discussed, presenting also the corrections suggested in recent works, which account for the fact that electron trajectories are not linear, and also involve backscattering losses which may reduce the recorded experimental intensities. Simple Si K ionization cross sections were measured through this approach, validated through a good agreement with values found in the literature. The advantages and disadvantages of the method are discussed and its application is extended to the determination of Si multiple ionization cross sections, where the very low emission rates (around two orders of magnitude lower than the single ionization case) make the use of the thin-target method impracticable.The corrected integro-differential method has also been used for the Ag and Sn L subshells, and compared in the case of Ag with previous results obtained through the thin-target approach. In all cases, characteristic intensities are assessed by using the parameter refinement software POEMA [4] developed previously; as this assessment is based on the integration of the ionization depth distribution function, a new methodology is proposed, since in the final expressions used the ionization cross section appears as a separated factor, which of course can be readily optimized.