A Procedure to Quantify Contributions to the Total Cross Section by Mechanisms Competing to the Direct Ionization

摘要

Experimental quantitative analysis by PIXE (particle induced X-ray emission) is highly dependent on thecomposition of the substrate. It is known that highly ionized projectiles change the effective ionization in a collisionwith a specific atom. Particularly, 2P vacancies on the projectile ion can be produced within the sample and thesevacancies will eventually be shared with the target atoms in the substrate, modifying the X-ray yield of the target.Therefore, it is of uttermost importance to account for these second order effects in the X-ray cross section to obtain anaccurate result for a PIXE analysis. In this paper, it is proposed a new procedure to estimate quantitatively thecontribution to the total ionization cross section of each effect: the direct and enhancement ionizations. FollowingVerma et al. (Nucl. Instr. and Meth. B245 56-60, 2006), it is modeled the total ionization cross section in asubstrate by an exponentially decaying term that represents the enhancement ionization contribution, and a linearlygrowing term that represents the induced ionization contribution. Estimation of the parameters in the model can beobtained directly from irradiation of targets with different thickness.