2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/159681Study of the fusion reactions between hydrogen isotopes in muonic molecules is the first example of the accurate accounting of the nucleus charge screening by a muon in the fusion process. At LUNA installation the measurements of astrophysical reaction cross sections were extended down to collision energies of a few keV. The screening by atomic electrons of the target became substantial. The possibility to look over screening from unbound electrons is given by metal-hydrides used as targets in dd reaction measurements. The classical Debye screening in plasma, applied to quasi-free electrons in metal, provides an explanation of unexpectedly large screening potentials found for some metals in the research through the Periodic table of elements.9 pages, 7 fugures, talk at the International Conference on Muon Catalyzed Fusion and Related Topics (muCF-07), Dubna, Russia, June 18-21, 2007Nuclear Theorytext