The scientific community has been occupied with research into super-heavy elements and the extension of the Periodic Table of Elements for over fifty years. Occasionally, the topic makes headlines when the International Union of Pure and Applied Chemistry (IUPAC) announces the discovery of new elements and grants the primacy of these discoveries to a specific research group, normally related to a large research center in countries such as the USA, Russia, Germany and Japan. Along with the prestige, the group is granted the honor of naming the new element.
IUPAC has recently published the following announcement, regarding elements number 113, 115, 117 and 118:
The announcement ends with the following paragraph:
Laboratories are already working on searches for the elements in the 8th row of the periodic table, and they are also working to consolidate the identification of copernicium and heavier elements. To be able to evaluate this work, IUPAC and the International Union of Pure and Applied Physics (IUPAP) are currently reviewing the selection principle and operations of a future Joint Working Party (JWP) and as soon as these principles have been decided a new group will be formed. This new JWP will review new claims and the consistency of new results with those already evaluated by earlier JWPs.
Perhaps, behind this somewhat vague wording, is hidden the unique story of element 112 (copernicium), and the deep controversy related to the contradicting claims for the primacy of its discovery. The story is about a group of scientists, who claimed to have discovered, by means of an original and innovative methodology, element 112 with 160 neutrons - back in 1971. In addition, they claimed they had come closest ever to the core of the "island of stability". They are the first and only scientists so far to make this claim. Their research was conducted by the Israeli physicist, native of Jerusalem, Prof. Amnon Marinov.
Element 112: Background and history
In 1966, Glenn Seaborg, one of the leading scientists at that time, published a theory claiming that beyond the heaviest known elements in the periodic table, which are short-lived and decay quickly, exist even heavier elements, predicted to be long lived and to have a stable nature. Seaborg called them the "island of stability". The riddle of the "island of stability" excited the curiosity of nuclear scientists and triggered a race for the discovery of long-lived super-heavy elements.
"The mainstream research approach focused on using particle accelerators in order to create nuclear reactions and discover artificially super-heavy elements, with atomic numbers above 110," says Prof. Stelian Gelberg, Amnon Marinov's last PhD student and one of his close collaborators. "To that aim, large-scale investments were made in the USA, Russia, Germany and Japan in order to build and upgrade powerful accelerators. New elements have been discovered, including recently. These elements are relatively short-lived and decay within seconds or fractions of a second," he explains.
Over a period of forty years, Prof. Marinov and his collaborators carried out their original and independent super-heavy elements research. Their study began back in 1971. Employing simple and low-cost means, they claimed to have discovered evidence for element 112. The nuclei they claimed to have discovered were completely different from known nuclei, and remained stable for forty-seven days (half-life time). Their extraordinary and unexpected stability was explained by their deformed shape and the number of neutrons they had.
Twenty-five years later, in 1996, a team of researchers from GSI Helmholtz Centre for Heavy Ion Research in Germany (GSI), led by Prof. Sigurd Hoffman, succeeded in discovering element 112 with 165 neutrons. Their experiment was conducted in the customary method. Using a particle accelerator, they created a reaction between zinc and lead nuclei. The isotope they discovered had 112 protons. It decayed immediately - its half-life time was less than 1/1000 of a second.
Scientific research normally progresses via its own internal means and methodologies. It is a rare and unnatural situation that scientific achievements depend on committees' reports in order to be acknowledged and accredited. The unique character of the super-heavy research field, being prestigious, highly competitive and extraordinarily complex, created this unusual conduct.
The primacy of the discovery of element 112 was highly controversial.
In 2009, a joint committee of IUPAC and IUPAP decided to grant the primacy to the GSI. Amnon Marinov and his collaborators did not deny the GSI's discovery, but appealed against this decision, claiming that they have discovered element 112 twenty five years earlier. Their appeal was dismissed. Therefore, the GSI research group was given the honor of naming element 112. The name copernicium was chosen.
Science does not stop. "The existence of stable states in nuclei, with an extremely high or extremely low number of neutrons, has been proved recently by various researchers, as Marinov claimed for decades," explains Prof. Gelberg. "These findings, which were achieved both theoretically and experimentally, reinforce Marinov's results related to super-heavy elements, and reinforce his claim for the discovery of element 112."
This amazing and unique story, which has not yet reached its conclusion, was recently made into a popular-science style documentary film by Rama Marinov-Cohen, Amnon Marinov's daughter. After his passing, while going through his archives, she felt that his research story must be made public. Prof. Gelberg and other collaborators of Prof. Marinov rolled up their sleeves and undertook the mission enthusiastically.
"I am not a scientist," she says, "but I feel I need to speak on what I believe is my father's behalf." The film is called "Element 112, The Marinov Affair".
Targeting the wider public and using 3D animations, the film illustrates the mainstream approach to creating nuclear reactions, as well as Marinov's original method. In addition, it provides a rare opportunity to reveal a fragment of the conduct of a powerful scientific community that is usually hidden from public sight.
"There is now an opportunity to highlight the pioneering studies of my father and his collaborators, and also to tell the story of their heroic struggle within the scientific community," she says. "Hopefully sooner rather than later, their 1971 discovery will be acknowledged."
The writer of this article took part in the making of the documentary.