Electron screening constraints for the cold fusion

The observation of an enhanced electron screening effect in the 2H(d,p)3H and 2H(d,n)3He reaction taking place in deuterated metallic targets may be a breakthrough for explaining the phenomenon of cold fusion. Based on our experimental results, theoretical calculations of screening energies for five different target materials (C, Al, Zr, Pd, and Ta) have been performed within an improved dielectric function theory. The theory, including polarization of both quasi-free and bound electrons, describes the observed target material dependence of the screening energies qualitatively correctly, underestimates, however, the absolute values by about a factor of two. Applying an effective screening energy approach and realistic stopping power values, the theoretical cross sections, thick target yields as well as nuclear reaction rates have been calculated down to the energies corresponding to the conditions of cold fusion experiments. This allows for a comparison of the experimental results at higher energies with those achieved in the heavy-water electrolysis experiments. Constraints for the cold fusion reaction rates and the energy production arising from tho experimental screening energies are discussed. (authors)