Experimental determination of multiple ionization cross sections in Si by electron impact

Abstract

The thin sample method is often used to experimentally determine ionization cross sections, especially when focusing on the low overvoltage region. The simplicity of the formalism involved in this method is very appealing, but some experimental complications arise in the preparation of thin films. In this work, a thick sample method was used to measure the Si-K x-ray production cross section by electron impact. The good agreement between the results obtained and the values reported in the literature validates the method and the parameters used. 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 sample method impracticable.

Experimental determination of total M shell and subshell X-ray production cross sections for uranium by proton impact

“…The uncertainties in the X-ray production cross-section were found by propagating the errors in eqn (4) as described in a previous work. 15 For this matter, the uncertainty associated with the mass stopping power was 10%; 23,24 the uncertainty of the mass attenuation coefficients was 10% because the X-ray energy range of interest is close to the M i absorption edges. 25 The uncertainty in the intrinsic efficiency of the SDD was estimated as 7%, as stated by Limandri et al 20 The overall average relative uncertainty for the obtained cross-sections was 13%, with a peak value of 15% observed for subshells linked to low-intensity X-ray lines, and a minimum of 9% for the M 5 subshell cross-sections.…”

“…For instance, with electron impact for: Ni 5 and Si 6 K shell cross sections; Ag L subshell cross sections; 7 and for multiple ionizations in K and L shells. 8 In the case of proton bombardment, the method was employed for: total L shell ionization cross sections of Sr and Mo; 9 Mo L subshells ionization cross sections; 10 K shell cross sections on elements with Z = 26–30 using low energy protons; 11 K, L and M shell production cross sections of Cu, Ag and Au, respectively; 12 and L and M shell cross sections of heavy elements, 13 among others. It was also used for determination of the Kα line cross section induced by heavy ion bombardment, 14 although in that work the authors used a different approach to the calculations than the rest of the cited articles.…”

“…In this approach and following a similar notation as in Pérez et al , 15 the X-ray production cross section when a thick sample is irradiated with protons of incident energy E 0 can be obtained from…”

Structure of the Fe and Ni L X-ray spectra

“…It can be seen that N q is independent of DE for a reasonable choice of this energy step length. 10 It is clear that this integral has energy units and is proportional to the total number of measured characteristic photons P q .…”

Experimental x-ray-production cross sections for the M3, M4 , and M5 subshells of Pt and Au by electron impact

“…To avoid the experimental difficulties for furnishing such thin samples and to overcome the uncertainties introduced by the backscattered contribution produced in the supporting substrate, a thick target method can also be implemented [18]. This approach has the additional advantage of being suitable in low-statistics experiments, such as the determination of multiple-ionization cross sections [19]. However, this thick-target method relies on certain assumptions that are not always suitable, particularly in the case of heavy elements; e.g., electron trajectories are assumed to be linear within the sample and backscattering losses are not taken into account.…”