Historical research guide · 0833 · 2006
Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces
A. Widom · L. Larsen
In one minute
Allan Widom and Lewis Larsen propose a route to nuclear reactions inside a hydrogen-loaded metal that never has to push two positive charges together. Their first step is the weak interaction: a proton that captures an electron becomes a neutron and a neutrino, and no Coulomb barrier stands in the way of that. The catch is mass — an ordinary electron is far too light, and needs about two and a half times its rest mass for the reaction to go. Widom and Larsen argue that on the surface of a loaded metal it gets exactly that. A packed layer of protons oscillates together, the local electric field reaches a hundred billion volts per metre or more, and electrons riding in that field are dressed up to roughly twenty times their vacuum mass, well past the threshold. The neutrons that follow carry almost no momentum, so neighbouring nuclei swallow them at once, and the authors trace the reaction chains and the energy each one releases.
Connection
Chapter 12 is about getting nuclear work out of a loaded metal lattice at ordinary temperatures, and this is the most-cited theory of how the field at such a surface could arrange it — the same hinge the thesis turns on, that changing the local electromagnetic environment changes what nuclei can do. Chapter 2 is about the field itself, and here the electron’s mass is computed from the difference between the photon propagator in condensed matter and the photon propagator in vacuum.
From the source
A proton that captures a charged lepton produces a neutron and a neutrino, and there is no Coulomb barrier to this weak-interaction process — the Coulomb attraction between the electron and the nucleus actually helps it along. The one requirement is a threshold: the lepton’s mass energy must exceed the neutron-proton mass difference of about 1.293 megaelectronvolts, which is 2.531 times the electron rest mass. The muon clears it by a wide margin; an electron at its vacuum mass does not.Introduction, Equations 1 to 3
The electron mass in condensed matter is shifted upward by local electromagnetic field fluctuations, and the shift is defined rigorously as the difference between the photon propagator in the presence of condensed matter and the photon propagator in vacuum, so that the vacuum fluctuations already carried in the physical electron mass are subtracted out. Written in terms of the electric-field spectral function the enhancement factor is manifestly gauge invariant, and the same mass-growth rule is the one used when laser fields dress an electron.Electromagnetic field fluctuations section, Equations 5 and 7 to 15
On a highly loaded palladium hydride surface a full proton monolayer oscillates collectively, and neutron-scattering data on protons in palladium put the resulting electric field at the scale of 1.4 times ten to the eleventh volts per metre, giving an electron mass enhancement factor of about 20.6 — far above the 2.531 threshold. Surface protons can therefore capture a heavy electron and produce an ultra low momentum neutron plus a neutrino; for deuterium the corresponding threshold is 6.88 and one capture yields two such neutrons.Proton oscillations section, Equations 18 to 25; the neutron production reaction, Equation 24
Because the neutrons are produced at very low momentum, that is at very long wavelength, their absorption cross sections are very large — inversely proportional to neutron velocity — so nearby nuclei absorb them efficiently, very few escape the immediate vicinity, and they will rarely be detected experimentally. The authors argue this can build neutron-rich nuclei in substantial quantities.Proton oscillations section, numbered comment (vii) following Equation 24
The neutrons then drive reaction chains in neighbouring matter with computed heats of reaction: lithium-6 capturing two neutrons through lithium-7 and lithium-8 to beryllium-8 and on to two helium-4 nuclei releases about 26.9 megaelectronvolts; helium-4 capturing two neutrons back to lithium-6 releases about 2.95 megaelectronvolts, closing a cycle; the direct lithium route to helium-4 plus helium-3 releases about 4.29 megaelectronvolts; and the largest single step is the lithium-8 beta decay at about 16.003 megaelectronvolts. Because the weak interaction has no barrier to cross, the authors note that helium-4 among the products does not by itself require direct deuterium-deuterium fusion.Low energy nuclear reactions section, Equations 26 to 31 and the closing summary
The authors name the engineering levers for the effect: an enforced chemical-potential or pressure difference across a palladium surface packs the surface into the single compact layer the coherent oscillations need; nearly isotopically pure hydrogen or deuterium systems are required because only those support the collective motion; the breakdown of the Born-Oppenheimer approximation at a surface is what allows the large fluctuations; and laser light of an appropriate frequency incident on the palladium surface, launching surface plasma waves, can amplify the proton oscillations and so enhance the production of catalytic neutrons.Proton oscillations section, numbered comments (i) and (iii) to (vi) following Equation 24
The way in
https://doi.org/10.1140/epjc/s2006-02479-8How to cite it
A. Widom, L. Larsen (2006) Ultra low momentum neutron catalyzed nuclear reactions on metallic hydride surfaces doi:10.1140/epjc/s2006-02479-8