Blog 23 Nuclear Excitation by Electron Capture (NEEC)

Blog written by Mark Kingston Levin PhD scientist and award -winning author of 30th Century: Escape.

Atomic Physics Discovery by Jeff Carroll of the US Army Research Lab and Christopher Chiara of Oak Ridge.

Figure 1. Jeff Carroll of the US Army Research Lab and Christopher Chiara of Oak Ridge are shown above.

Scientists have seen evidence of electron capture by the nucleus for the first time in history. This electron capture results in nuclear excitation that could lead to an energy storage capacity 100,000 times that of the best batteries.

This data confirms the theoretical prediction made more than forty years ago. The team, headed by Jeff Carroll and Christopher Chiara, excited an atomic nucleus by electron capture and then observed the decay processes of the nucleus.

Electrons orbiting an atom some distance away from the nucleus are not normally captured; however, inner-shell electrons have a finite probability of being inside the nucleus. A well-known decay called internal conversion can transfer energy to such an electron, causing it to be ejected from the atom.

Figure 2 (a-e). Nuclear Excitation Electron Capture (NEEC) recombination mechanism of exciting an electron into the K shell of a bare ion, followed by the radiative decay of the nucleus. The figures above depict the electronic transition and the nuclear excitation. In Figures (a) to (b), the nucleus is schematically represented as undergoing the transition from the ground state (G) to the excited state (E). Figures (c) and (d) show the nucleus returning to the ground state.

NEEC is a two-step mechanism that transitions an electron into the K shell of a bare ion, followed by the radiative decay of the nucleus. The illustrations in Figure 2 depict the electronic transition. In the figures (a) and (b), the nucleus is schematically represented as undergoing the transition from the ground state (G) to the excited state (E). The nucleus returns to the ground state through a two-step process shown in the figures (c) and (d).
Electron capture by the nucleus may be thought of as the reverse of internal conversion. Theoretical scientists have been discussing its existence for about four decades. The absorption of a free electron by a hole in a normally filled atomic shell is sometimes called THE FIRST STEP. Nuclear excitation may occur if the electron’s initial energy plus its atomic binding energy equals the energy difference between two nuclear states. While the theory seems clear and easy, the energy-matching has made NEEC a very difficult process to produce experimentally.
Jeff Carroll and Christopher Chiara of the US Army Research Laboratory in Adelphi, Maryland produced atoms of the radioactive isotope molybdenum-93. Next, the team added electrons of an energy state that they believed would cause NEEC. Carroll and Chiara showed that if the nucleus did become excited through the NEEC process, the decay products would be different to those of an excited nucleus. The team measured the decay sequences involved, analyzing the gamma ray spectrum from decay products with differing half-lives. As expected, the measurements matched up with the theoretical predictions of the unique decay sequence of an excited molybdenum-93 nucleus.

The research is described in more detail in the February 8 issue of Nature.

An illustration of an excited nucleus giving off energy for an isotopic battery

An illustration of an excited nucleus giving off energy for an isotopic battery

Jeff Carroll and Christopher Chiara of the US Army Research Laboratory in Adelphi, Maryland produced atoms of the radioactive isotope molybdenum-93. Next, the team added electrons of an energy state that they believed would cause NEEC. Carroll and Chiara showed that if the nucleus did become excited through the NEEC process, the decay products would be different to those of an unexcited nucleus. The team measured the decay sequences involved, analyzing the gamma ray spectrum from decay products with differing half-lives. As expected, the measurements matched up with the theoretical predictions of the unique decay sequence of an excited molybdenum-93 nucleus.

The research is described in more detail in the February 8 issue of Nature.

Dr. Levin

Dr. Levin was born and grew up in Vermont with many winters spent in Florida as a child. As a teenager he wrote poetry, served as a lifeguard and played football. He currently enjoys sailing, exploring underwater caves, snorkeling, writing science fiction and other pursuits. After working on the Apollo and Mars projects, he returned to school to study under Nobel Laureate Paul Dirac, obtaining his PhD in 2.5 years. Dr. Levin founded two companies and served the science policy apparatus in President Ford’s administration. He has been published over 44 times in scientific literature and was awarded over 32 US patents. The science fiction writer is now emerging with his first work, a trilogy entitled 30th Century. The first award-winning book, 30th Century: Escape, is currently available on Amazon. Book two in the series, 30th Century: Revived, should be released before the end of April 2018.

2018-12-10T22:06:28+00:00 March 30th, 2018|Blog|