Multiple ionization by electron, positron, proton and antiproton impact in rare gases

C. C. MONTANARI

Fort Worth

Congreso; 24th International Conference on the Application of Accelerators in Research and Industry (CAARI 2016); 2016

University of North Texas, Sandia National Laboratories, y Los Alamos National laboratory

We present a comparison of multiple ionization cross sections by impact of electrons, positrons,protons and antiprotons, including our theoretical results [1,2] and a detailed compilation ofexperimental data for these |Z|=1 projectiles and four different targets. We consider the rare gases Ne,Ar, Kr and Xe, and final charge states from +1 to +3 (Ne), +5 (Ar) and +6 (Kr and Xe).Our theoretical development relies on three approximations:1. The independent particle model (IPM): the ejected electrons ignore the fate of each other,neglecting the correlation in the final state. The probability of MI is expressed as a multinomialcombination of independent ionization probabilities.2. The continuum distorted-wave eikonal initial state approximation adapted in the case of lightparticles, such as electrons or positrons, to take into account the finite momentum transferred, thenon-linear trajectory, and the energy threshold for the multiple ionization. The energy thresholds forelectron and positron impact have been calculated separately and imposed within the multinomialexpansion.3. The post-collisional ionization due to Auger type processes is independent of the projectile. Thus, itis included in a semi empirical way by incorporating the experimental branching ratios of the chargestatedistribution after a single initial vacancy.We obtained good results for quadruple, quintuple and sextuple ionization cross sections. This isrelated to the good description of the deep-shell contribution and the influence of Auger typeprocesses in the final charge state [3]. For highly-charged ion production by light particles, the postcollisional ionization is the dominant ionization channel in the whole energy range, even close to thethreshold. Unfortunately the particle-antiparticle comparison can be made up to triple ionizationbecause there are no experiments for higher levels of multiple-ionization.[1] Montanari C C and Miraglia J E, 2014, J. Phys. B 47, 105203.[2] Montanari C C and Miraglia J E, 2015, J. Phys. B 48, 165203.[3] Tavares A C et al, 2014, J. Phys. B 48, 045201