Low energy nuclear reactions in solids

The interplay between a nucleus and its environment is known to play an important role in nuclear reactions when the incident energy has been reduced far below the Coulomb barrier, where the cross section described by the Gamow function decreases drastically due to the steep drop in the quantum mechanical penetration of the barrier. For the fusion reactions in metals, experimental techniques were developed in which target nuclei were implanted in a metal. The DD fusion reactions were studied, so far, and an enhancement in the rate of the D(d, p)T fusion reaction over the Gamow function was found for deuterons in Ti and Yb. Here we report on further measurements of the D+D reactions in other materials. Of particular interest is the fact that the reaction rate of the D+D reactions at 2.5 keV in PdO is 50 times larger than in Ti, and the deduced screening potential amounts to 600 eV. This cannot be explained by bound-electron screening which may give a potential of 20 eV at most, but suggests the existence of an additional, and important, mechanism. Perhaps there is a fluidity of deuterons in metals that also reduces the Coulomb barrier between the interacting deuteron pair. An exhaustive study of nuclear reactions in metal would be very significant; one would then not only simulate nuclear fusion reactions in a stellar plasma where the nuclei are immersed in a sea of electrons, but also explore the limitations of nuclear fusion at room temperature. (author)