- Widom-Larsen theory proposes that "heavy electrons" formed at the surface of palladium deuteride react with deuterons to form di-neutrons (d+ + e- -> 2n) with "ultra low momentum," and thus very high capture cross-section. These neutrons can then cause transmutation and energy release. It is claimed that this is not "fusion," but the effect is that a deuteron has been broken into pieces, which are then, so to speak, spoon fed to nuclei one at a time. That this is not "fusion" is purely a semantic distinction; the fuel is deuterium, the electrons are catalytic, overall, and the result is heavier isotopes with energy released. This theory has been heavily promoted by Steve Krivit, of New Energy Times, who has criticized the work that has led most in the field to conclude that the heat/helium balance indicates some kind of deuterium fusion. W-L theory, however, does not account for the isotopic distribution of alleged transmutation products found with cold fusion: Helium predominates (there is no doubt about that, the only question is the exact ratio, which would be dependent on the mix of reactions caused. Isotopic ash is found only at levels far below that of helium.
Most in the field think that the main reaction, whatever it is, produces only helium and energy, and that other products, such as neutrons, tritium, other transformed elements, and X-rays are the product of secondary reactions or rare branches. However, W-L theory still receives some level of positive comment, most notably, recently, from a scientist working in the government who was apparently happy to call his work "not fusion" because of W-L theory.