Editing Cold fusion (section)

===Lack of expected reaction products===
Conventional deuteron fusion is a two-step process,<ref group="text" name="branching_and_gamma" /> in which an unstable high-energy [[Reaction intermediate|intermediary]] is formed:
:[[deuterium|{{sup|2}}H]] + {{sup|2}}H → [[Alpha particle|{{sup|4}}He]][[Nuclear isomer|{{sup|*}}]] + 24 [[MeV]]
Experiments have shown only three decay pathways for this excited-state nucleus, with the [[Branching fraction|branching ratio]] showing the probability that any given intermediate follows a particular pathway.<ref group="text" name="branching_and_gamma"/> The products formed via these decay pathways are:
:{{sup|4}}He{{sup|*}} → [[neutron|n]] + [[Helium-3|{{sup|3}}He]] + 3.3 MeV ([[Branching fraction|ratio]]=50%)
:{{sup|4}}He{{sup|*}} → [[proton|p]] + [[Tritium|{{sup|3}}H]] + 4.0 MeV (ratio=50%)
:[[Isomeric transition|{{sup|4}}He{{sup|*}} → {{sup|4}}He]] + [[gamma particle|γ]] + 24 MeV (ratio=10{{sup|−6}})
Only about one in a million of the intermediaries take the third pathway, making its products very rare compared to the other paths.{{sfn|ps=|Schaffer|1999|p=2}} This result is consistent with the predictions of the [[Bohr model]].<ref group="text" name="consistent"/> If 1 watt (6.242 × 10{{sup|18}} eV/s){{refn|group="notes"|name=watt-ev|refn=1 W = 1 J/s ; 1 J = 6.242 × 10{{sup|18}} eV since 1 eV = 1.602 × 10{{sup|−19}} joule}} were produced from ~2.2575 × 10{{sup|11}} deuteron fusions per second, with the known branching ratios, the resulting neutrons and tritium ({{sup|3}}H) would be easily measured.{{sfn|ps=|Schaffer|1999|p=2}}{{sfn|ps=|Huizenga|1993|pp=7}} Some researchers reported detecting {{sup|4}}He but without the expected neutron or tritium production; such a result would require branching ratios strongly favouring the third pathway, with the actual rates of the first two pathways lower by at least five orders of magnitude than observations from other experiments, directly contradicting both theoretically predicted and observed branching probabilities.<ref group="text" name="branching_and_gamma" /> Those reports of {{sup|4}}He production did not include detection of [[gamma ray]]s, which would require the third pathway to have been changed somehow so that gamma rays are no longer emitted.<ref group="text" name="branching_and_gamma" />

The known rate of the decay process together with the inter-atomic spacing in a [[metallic crystal]] makes heat transfer of the 24 MeV excess energy into the host metal lattice prior to the intermediary's decay inexplicable by conventional understandings of [[momentum]] and energy transfer,<ref>{{harvnb|Scaramuzzi|2000|p=4}}, {{harvnb|Goodstein|1994}}, {{harvnb|Huizenga|1993|pp=207–208, 218}}</ref> and even then there would be measurable levels of radiation.<ref>{{harvnb|Close|1992|pp=308–309}} "Some radiation would emerge, either electrons ejected from atoms or X-rays as the atoms are disturbed, but none were seen."</ref> Also, experiments indicate that the ratios of deuterium fusion remain constant at different energies.<ref name="Huizenga_chemical_environment">{{harvnb|Close|1992|pp=268}}, {{harvnb|Huizenga|1993|pp=112–113}}</ref> In general, pressure and chemical environment cause only small changes to fusion ratios.<ref name="Huizenga_chemical_environment" /> An early explanation invoked the [[Oppenheimer–Phillips process]] at low energies, but its magnitude was too small to explain the altered ratios.{{sfn|ps=|Huizenga|1993|pp=75–76, 113}}