THE LEVINE-MERMIN DIELECTRIC FUNCTION TO DESCRIBE STOPPING OF INNER-SHELLS

J. P. PERALTA; A. M. P. MENDEZ; C. C. MONTANARI

Congreso; International Symposium on Swift Heavy Ions in Matter (SHIM) & International Conference on Atomic Collisions in Solids (ICACS); 2022

The shellwise local plasma approximation (SLPA) has been successfully used to deal withthe stopping power due to excitation and ionization of bound electrons [1]. However, for multielectronicrelativistic targets (atomic number greater than 54) an overestimation is noted forhigh impact energies [2]. New measurements in tungsten [3] confirm these differences. Inthis contribution, we present an improvement of this formalism by using the Levine-Mermin[4, 5] dielectric function (SLPA-LM). This approach considers a more realistic description ofthe bound electrons by facing the problem of the damping in the collective excitations. Weintroduce local damping that depends on the density of electrons of each shell, keeping thefull-theoretical characteristic of the SLPA. To analyze the dependence of the SLPA-LM withthe number of sub-shells we use this model to calculate stopping cross sections S(v) for protonimpact on metal targets of group VI of the periodic table (Cr, Mo and W). We also include resultsof stopping for Hf to highlight the importance of the SLPA-LM description on relativistictargets.The results are presented as stopping number L, which is proportional to v2S(v) to seethe high energy region enlarged. Figure 1 shows the improvement obtained. As expected theSLPA-LM improves the Levine-Lindhard model in [1, 2]. We observe that this changes theresults for targets with many bound shells, while changes are negligible for targets such as Crwith fewer shells.