Historical research guide · 0493 · 2012
Bird’s Eye View of Phonon Models for Excess Heat in the Fleischmann–Pons Experiment
Peter L. Hagelstein
In one minute
This short 2012 review is Peter Hagelstein’s compact statement of the problem and of his group’s answer to it. The problem first. In the Fleischmann–Pons experiment the heat is prodigious — hundreds to tens of thousands of electron-volts for every palladium atom in the cathode, far beyond anything chemistry can supply — and the helium-4 that appears tracks the energy at a ratio near 24 million electron-volts per helium atom. Yet the fast particles that a textbook nuclear reaction would throw out are not there in matching numbers. Hagelstein’s reading of a neutron-counting argument is that each helium is born with less than twenty thousand electron-volts of that 24 million. So the energy leaves by another road. His candidate is fractionation: a coherent process that takes one 24 MeV quantum and divides it into roughly four hundred million vibrational quanta of about sixty milli-electron-volts each. Ordinary models cannot do that, because their many indirect pathways cancel; add loss at the right frequency and the cancellation lifts.
Connection
Chapter 12 rests on the lattice being a participant in the nuclear reaction rather than a passive container, and this is the short paper that says why that has to be true if the heat is real. It also names the mechanism the rest of the programme exists to test — the fractionation of one large nuclear quantum into hundreds of millions of vibrational quanta — and the bench experiment that would show it directly.
From the source
The excess heat effect in the Fleischmann–Pons experiment is prodigious: referenced to the number of atoms in the cathode, the reported energy runs from hundreds to tens of thousands of electron-volts per palladium atom, with no chemical reaction available that could produce so much, and high deuterium loading is important to seeing it at all.Section 2, Absence of energetic particles
Helium-4 in the gas is correlated with the energy produced at a ratio near 24 MeV per helium atom, as found by Miles, Bush and coworkers; and because fast helium would knock deuterons into secondary fusion and produce neutrons readily even at modest energy, while hardly any neutrons are seen in cells producing excess energy, the helium must be born with less than twenty keV of that 24 MeV.Section 2, Absence of energetic particles, closing paragraph
The two-laser experiment points to where the energy goes first. Excess heat can be stimulated with a single weak diode laser but generally does not persist once the laser is off; stimulated with two weak diode lasers it responds to the difference frequency and generally does persist, with the strongest responses correlated with compressional optical phonon modes of zero group velocity — consistent with the nuclear energy being channelled into hybrid plasmon and optical phonon modes that are low-loss near 8, 15 and 21 THz.Section 3, Two-laser experiment; Section 13, Making phonons
The quantitative statement of the puzzle: converting 23.85 MeV into optical phonon modes at 15.1 THz, that is 63 meV apiece, requires the production of about 3.78 times ten to the eighth quanta. There is no precedent for such an effect, and if it exists the new mechanism of the Fleischmann–Pons effect becomes reconcilable with nuclear and condensed matter physics.Section 4, Fractionation of a large quantum
What blocks fractionation in the ordinary spin–boson model is destructive interference: indirect coupling between distant resonant states proceeds through all possible pathways and the cancellation is almost perfect. Adding loss at the transition frequency of the two-level system removes it, and the resulting lossy model fractionates a large quantum efficiently, with the coupling strength linear in the local phonon exchange matrix element, going as the square root of the oscillator excitation and roughly linearly in the number of two-level systems — so the leverage is in having very many of them working together.Sections 5 and 6, Energy exchange between two-level systems and an oscillator, and Lossy spin–boson model and coherent energy exchange; Section 7, Excitation transfer
The material picture is testable. Because the electron density in bulk palladium deuteride is too high for molecular deuterium to form, the model places the reaction at palladium monovacancies produced by inadvertent codeposition in the outer 100 to 300 nanometres of the cathode, which fits the onset of excess power above a loading near 0.80 and a temperature dependence whose activation energy, 670 meV as Storms measured, matches helium diffusion in palladium. The named next measurement is a Raman experiment detecting the relative strength of the sidebands during excess power production in a two-laser cell, which would show directly whether the nuclear energy is going into those modes.Sections 12, 13 and 14, D2 and vacancies, Making phonons, and Getting the helium out
The way in
https://doi.org/10.70923/001c.72169How to cite it
Peter L. Hagelstein (2012) Bird’s Eye View of Phonon Models for Excess Heat in the Fleischmann–Pons Experiment doi:10.70923/001c.72169