[Reading Science] "We Need to Rewrite Existing Theories"... Surprising Discovery by Japanese Scientists

Successful First Detection of Oxygen-28 Isotope
Contrary to Existing Theories, It Decays Immediately
"Atomic Structure Stability 'Magic Number' Must Be Revised"

Japanese scientists have succeeded for the first time in creating the theoretically predicted oxygen isotope (oxygen-28, 28O). However, the discovery that existing atomic structure theories in physics may need to be rewritten has attracted attention.

A research team from Tokyo Institute of Technology in Japan published a paper on this on the 30th (local time) in the international academic journal Nature. Oxygen (O) is known to have a nucleus composed of 8 protons and 3 to 18 neutrons, and so far, the existence of 15 isotopes has been identified. Among these, three stable isotopes found in nature have neutron numbers of 8, 9, and 10, namely 16O, 17O, and 18O. Of these, 16O accounts for 99.8% of the total, making it the majority. The remaining 12 isotopes are unstable isotopes with short half-lives due to radioactive decay.

The research team used the superconducting heavy-ion accelerator (RIBF) at the RIKEN Institute in Japan to create and detect oxygen-28, which has 20 neutrons, for the first time in history. The team first fired a calcium-48 isotope beam at a beryllium target to produce fluorine-29 isotopes. Fluorine-29 has one more proton than oxygen-28 but the same number of neutrons, 20. Then, the team collided fluorine-29 isotopes with a thick liquid hydrogen target, causing the ejection of one proton from the nucleus, successfully generating oxygen-28.

The problem was that oxygen-28 (8 protons and 20 neutrons) decayed and disappeared immediately after being created, contrary to existing theories. This result differed from previous atomic structure theories. Scientists had believed that atomic nuclei with certain "magic numbers" of protons and neutrons would be more stable. For example, oxygen isotopes with neutron numbers of 2, 8, 20, 28, 50, 92, or 126 are less likely to decay, and stability is thought to double as these numbers increase. Accordingly, scientists predicted the existence of oxygen-28 and expected it to be a stable substance with a long half-life because it falls under the "magic number" category.

Instead, the research team could only detect the decay products oxygen-24 (24O) and four neutrons. Until a few years ago, only two neutrons could be measured simultaneously, making it impossible to confirm the creation of oxygen-28. However, by successfully observing four neutrons simultaneously, the team confirmed the production of oxygen-28. To achieve this, the team found RIKEN's own equipment insufficient and even rented special detectors from the GSI Helmholtz Centre for Heavy Ion Research in Germany. This equipment can capture the neutrons at the moment they collide with protons.

Takashi Nakamura, a researcher at Tokyo Institute of Technology, explained, "Although we could not measure the exact lifetime of oxygen-28, we confirmed that contrary to predictions of stability, it decays immediately upon creation."

The scientific community regards this as a revolutionary finding that may require rewriting existing atomic structure theories, although further verification is needed. Previously, in 2009, a research team from Saint Mary's University in Canada reported that another oxygen isotope, oxygen-24, which has 16 neutrons and does not fall under the "magic number" category, had a relatively long half-life of 61 milliseconds (ms; 1 ms is one-thousandth of a second). In the case of oxygen-24, the 8 protons and 16 neutrons are strongly bound, resulting in a relatively long lifetime, suggesting that the number "16" could also be considered a magic number under existing atomic structure theories.

Nature stated, "This research raises fundamental questions about the forces that bind atomic nuclei," and added, "The research team hopes to create and comparatively analyze another isotope, oxygen-30."