Multiply-charged ions collisions on He: evaluations of classical two-active electron models

BACHI, NICOLÁS; S. OTRANTO

Budapest

Conferencia; International Conference on Many Particle Spectroscopy of Atoms, Molecules, Clusters and Surfaces; 2018

P { margin-bottom: 0.08in; direction: ltr; color: rgb(0, 0, 0); }P.western { font-family: "Times New Roman",serif; font-size: 12pt; }P.cjk { font-family: "SimSun","宋体"; font-size: 12pt; }P.ctl { font-family: "Times New Roman",serif; font-size: 12pt; }A:visited { color: rgb(128, 0, 128); }A.western:visited { }A.cjk:visited { }A.ctl:visited { }A:link { color: rgb(0, 0, 255); }Wepresent a detailed evaluation of the physical picture provided byclassical 2-electron models for the He atom. Total cross sections(TCS) resulting from collision processes involving protons as well asmore highly charged projectiles are evaluated by means of twoclassical models that make use of the classical trajectory MonteCarlo method (CTMC). These models incorporate momentum-dependentpotentials to the He Hamiltonian in order to avoid the instabilitywhich is inherent to classical treatments of multielectron targets. Thefirst of these constraint potentials was introduced by Kirschbaum andWilets [1] and it is denoted Heisenberg core potential (HC). Theother was introduced by Cohen [2] and is referred to asenergy-bounded approach (EB). For both models, different authors haveconsidered different sets of parameters for the momentum-dependentterms based on particular derivations [1 ? 4]. Inthis work, following the criteria presented by Zhou et al [4],we propose a new set of values and analize their physicalimplications and the resulting total cross sections for collisionprocesses involving proton, C6+ and O8+projectiles. Asan example, in figure 1 we compare the TCS for single ionization(SI), single capture (SC), transfer-ionization (TI), and doubleionization (DI) for proton-He collision predicted by the HC-CTMC forthe set of parameters of this work (dashed line) to those obtainedwith the set introduced by Morita et al [3] (solid-line). Theimpact energy range explored was 10 keV ? 3000 keV. In Figure 2 weshow a similar analysis for the EB-CTMC model. In both cases, thecalculated TCS are benchmarked against the available experimentaldata [5]. General trends are similar for both descriptions with theexception of the SI channel which exhibits a strong dependence on theparticular values of the parameters. This fact is related to thefirst ionization potential predicted by these parameterizations.Figure 1. HC-CTMC cross sections fordifferent reaction channels in H+ + He collision as afunction on impact energy. Experiments: [5].Figure 2. EB-CTMC cross sections fordifferent reaction channels in H+ + He collision as afunction on impact energy. Experiments: [5].References[1]C. L. Kirschbaum and L. Wilets, Phys.Rev. A (1980)21, 834.[2]J. S. Cohen, Phys. Rev. A(1996) 54, 573.[3]S. Morita, N. Matsuda, N. Toshima and K. Hino, Phys.Rev. A (2002)66, 042719.[4]Y. Zhou, C. Huang, Q. Liao and P. Lu, Phys.Rev. Lett. (2012)109, 053004.[5]M. B. Shah and H. B. Gilbody, J.Phys. B: At. Mol. Opt. Phys(1985) 18, 899.