Nuclear Excitation by Electron Capture Observed in US Army Research Lab

Thanks to a reader for sending me a link to this article from Physics World which reports how a team of researchers at the US Army Research Laboratory have observed nuclear excitation by electron capture (NEEC) – where an atomic nucleus becomes excited when it absorbs an electron.

From the Article:

To make their observations, the team produced atoms of the radioactive isotope molybdenum-93 and had them absorb electrons of energy that they believed would cause NEEC. They predicted that if the nucleus did become excited, its sequence of decay products would be different to that of an unexcited nucleus. Determining the decay sequence involved analysing gamma-ray emissions from decay products with differing half-lives. As hoped, their measurements matched up with the theoretical predictions of the unique decay sequence of an excited molybdenum-93 nucleus.

One important consequence of the discovery is that it provides a possible explanation for the abundance of elements such as gold and platinum in the universe. If NEEC were a fairly common process in nature, then certain elements could transform into others after being created in stars. The team’s work could also lead to the development of new technologies that harness the energy of excited nuclei. This, according to Carroll, could lead to power sources with an energy density 100,000 times greater than that in chemical batteries.

The full research report has been published in Nature here.

  • Engineer48



    The atomic nucleus and its electrons are often thought of as independent systems that are held together in the atom by their mutual attraction.

    Their interaction, however, leads to other important effects, such as providing an additional decay mode for excited nuclear states, whereby the nucleus releases energy by ejecting an atomic electron instead of by emitting a γ-ray.

    This ‘internal conversion’ has been known for about a hundred years and can be used to study nuclei and their interaction with their electrons1,2,3.

    In the inverse process—nuclear excitation by electron capture (NEEC)—a free electron is captured into an atomic vacancy and can excite the nucleus to a higher-energy state, provided that the kinetic energy of the free electron plus the magnitude of its binding energy once captured matches the nuclear energy difference between the two states.

    NEEC was predicted4 in 1976 and has not hitherto been observed5,6.

    Here we report evidence of NEEC in molybdenum-93 and determine the probability and cross-section for the process in a beam-based experimental scenario.

    Our results provide a standard for the assessment of theoretical models relevant to NEEC, which predict cross-sections that span many orders of magnitude.

    The greatest practical effect of the NEEC process may be on the survival of nuclei in stellar environments7, in which it could excite isomers (that is, long-lived nuclear states) to shorter-lived states.

    Such excitations may reduce the abundance of the isotope after its production.

    This is an example of ‘isomer depletion’, which has been investigated previously through other reactions8,9,10,11,12, but is used here to obtain evidence for NEEC.”

  • Andreas Moraitis

    The term „electron capture“ is somewhat misleading in this context. As far as I understood it, in the proposed model the target nucleus ‘steals’ kinetic and atomic binding energy of a shell electron, which remains otherwise untouched and can finally escape. In contrast, “electron capture” stands usually for a process where a proton absorbs an electron, whereby a neutron is generated and both the proton and the electron disappear. So this paper has nothing to do with LENR theories that involve electron capture (e.g. Widom-Larsen, Godes, or Hunf).

  • cashmemorz

    This is the kind of research that has to be done to draw a more accurate picture of what is occurring inside atoms, so as to have a more realistic model of what is happening in stars. It will be only then, that we can expect to have a useful model of what might be happening in the processes required for stellar fusion to occur. There seems to be an attitude, that the requirements for hot fusion have been sufficiently understood, since the 1950’s, to decide that Earth based fusion can be attained. This explains, in large part, the reason why hot fusion has not been successful. The processes that are occurring in the Sun are too poorly understood to be able to use those processes as a base for doing hot fusion on Earth. And just one more reason why Randell Mills’ Theory should be closely examined by the hot fusion community. The Grand Unified Theory-Classical Quantum Physics, has enough in it to help hot fusion, and many other projects, to get going in a more realistic way.

  • ScienceFan

    I seem to remember that in Larry Niven’s expanded Ringworld universe, the humans were using ‘molecular distortion batteries’ with something like 10,000+ times the average battery chemical energy density, such that they could easily be turned into bombs when human settlements were attacked. NEEC batteries, maybe?

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