Atomic physics in the interaction of projectiles with plasmas

In a first work, we reanalyze the energy loss experimental data from Cayzac et al. [Nat. Commun. 8, 15693 (2017)] using our successful ion charge state theoretical model. Different projectile electron loss and capture processes are considered to estimate the projectile charge state. The projectile electron loss, or ionization, with plasma ions and free electrons are considered. On the other hand, the projectile electron capture, or recombination, with plasma free or bound electrons are also considered. The projectile ionization with plasma ions is shown as the main factor that modifies the mean charge of the projectile. Our charge state model fits better with experimental data than any other model in the bibliography. Thus, it should be considered in any charge state and any energy loss estimation to obtain reliable results in future works.

In the second work, stopping power because of free and bound electrons in a fully or partially ionized plasma will be studied. The free electron stopping power will be analyzed using the dielectric formalism, whereas bound electron stopping power will be calculated through atomic approximations. The data used for the calculations came from experiments in which hydrogen and argon hot plasmas are shot with up to 10 MeV protons. Plasma ion densities are ranged between 1019 and 1022 cm-3 and electron temperatures from 10 to 300 eV. In this experimental setup, the data show a regime of reduced stopping power that will be reproduced early exactly by our theoretical model.

In the last work, a method is proposed that accounts for the stopping power of free and bound electrons of a partially ionized plasma. To formulate this method, the well-known dielectric formalism is used, combining a dielectric function of quantum plasmas, which includes temperature, for free electrons, and the shellwise local plasma approximation (SLPA) for bound electrons. Since few experimental data are available for plasmas, our method calculations at T = 0 for solids are compared with SRIM code. The agreement with experimental data is excellent. Also, a cold gas target is considered at different ionization states; results show the expected behavior. Finally, our results for plasmas at diverse conditions of temperature are compared with other methods from the literature that contemplate bound electrons explicitly: Mehlhorn, Zimmerman and Unified Wave Packet models. Differences observed between our method, and Mehlhorn and Zimmerman models can be explained by the limited range of application of these old models. In contrast better agreement is obtained when our method is compared with Unified Wave Packet model. These comparisons also serve to prove the validity of our method in different elements.

Zoom-Meeting
https://gsi-fair.zoom.us/j/96629963798

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