Probing Neutrons and Purported Fission Daughter Products from Gas-Loaded, Laser-Irradiated Metal-Hydrogen Targets

This article reviews a series of experimental reports that claim the observation of energetic neutrons and the formation of new low-atomic number (Z ≤ 30) elements in solid-state metal-hydrogen samples in out-of-equilibrium conditions (created, e.g., via pressure/temperature cycling or laser irradiation). Reported new element formation is concomitant with morphological feature changes and, in some cases, new elements correspond to known fission daughter pairs of the involved metal lattice nuclei. Related experimental reports suggest that the elements found in the newly formed morphological features may have unnatural isotopic ratios, indicating a nuclear origin. The presented body of experimental reports suggests a hypothesized novel class of nuclear reactions, which has recently motivated the creation of a new research program by the US Department of Energy’s innovation agency ARPA-E. Because of the absence of high-energy stimuli in such systems, ARPA-E refers to this hypothesized class of nuclear reactions as low-energy nuclear reactions (LENR). To help interested parties quickly gain insights into this research domain, we present a curated collection of experimental evidence reported to date, provide a theoretical explanation that is both consistent with these reports and rooted in established physics, and lay out a research roadmap.