FULLY RELATIVISTIC STRUCTURE CALCULATIONS OF HEAVY TARGETS FOR INELASTIC COLLISIONS

C. C. MONTANARI; A. M. P. MENDEZ; D. M. MITNIK

Caen

Congreso; 10th International Symposium on Swift Heavy Ions in Matter (SHIM) & 28th International Conference on Atomic Collisions in Solids (ICACS); 2018

www.shim-icacs2018.org

We present fully relativistic structure calculations for Ta (Z=73), Pt (Z=78), Th (Z=90) and U (Z=92). The description of these many-electron atoms requires the solution of the relativistic Dirac equation. The method uses the parametric potential model to obtain a unique potential. This enables us to represent both bound and continuum states on the same footing, being of great interest for inelastic collisional calculationsThe description of heavy atoms requires the solution of the relativistic Dirac equation. To this end, we used the HULLAC code package [1], which allows one to obtain accurate relativistic one-electron orbitals and multiconfiguration bound states and energies. The calculations are based on first-order perturbation theory with a central field, including the contribution from the Breit interaction and quantum electrodynamics corrections. The detailed energy levels are computed using the RELAC code [2], which uses the parametric potential model. This model consists in minimizing the first-order relativistic energy of a given set of configurations for a parametric analytical function for the screening charge distribution. Although this code was written for calculations of highly charged ions, it can be successfully employed in other atomic systems, such as the ones presented here.First, we calculated the atomic structure with nonrelativistic andsemirelativistic approaches using the AUTOSTRUCTURE code [3]. We compared the computed binding energies of the bound orbitals with the experimental values in solid compiled by Williams [4].The nonrelativistic calculations showed large discrepancies with the experimental results, which probed the necessity of a relativistic approach.Then, the semirelativistic method was tested, allowing better agreement with the experimental binding energies. However, the large errors found for the most tightly bound inner orbitals evidenced the need of fully relativistic calculations.The binding energies obtained for Ta, Pt, Th and U using the fully relativistic method are shown with up-filled triangles in Fig. 1. The figure also includes the experimental bound energies (hollow circles) [4]. The values computed for the inner-orbitals agree with the experimental ones in about 2%. The discrepancies found with the more external shells are accounted for the structure differences between the atoms (computed) and the solids (experiments).Previous structure calculations for other atomic systems showed good description of relativistic targets in various inelastic collisions processes, particularly energy-loss and straggling [5].Further collisional calculations for these atoms are presented in the conference by one of the authors.[1] A. Bar-Shalom et al, J. Quant. Spect. Rad. Transf. 71, 169 (2001).[2] M. Klapisch, Comput. Phys. Commun. 2, 239 (1971).[3] N. R. Badnell,, J. Phys. B 30, 1 (1997).[4] G. Williams in http://xdb.lbl.gov/Section1/Sec_1-1.html[5] C. C. Montanari et al, Phys. Rev. A 80, 012901 (2009).