Interviewing Yuri Oganessian

The journey north from Moscow to the Joint Institute for Nuclear Research (JINR) takes two hours. Along the way there is the odd glimpse of a gold-domed Russian Orthodox church, a lot of road-construction activity, and then miles of peaceful forest. Every now and then, at the treeline, you pass a stall selling home-made produce – jars of jam and pickle, woodland berries and mushrooms.

“There was once nothing here besides the river and the forest,” explains 85-year-old Yuri Oganessian, upon my arrival in Dubna, the town that has grown up around JINR. “The institution was founded in 1956, and today there are 1200 scientists working here, from around the world.” Oganessian has been part of what is now named the Flerov Laboratory of Nuclear Reactions since its beginnings in 1957, first under Georgy Flerov, its founder, then as director himself, and today as scientific leader.

Over those six decades he been a key figure in exploring some of the most fundamental scientific questions – how many chemical elements are there? How can we make elements with heavier nuclei? And will some prove to be stable and long-lived?

Oganessian is currently the only living person to have an element named after him. It is number 118, which neatly completes the seventh row in the periodic table and is called oganesson. The accolade, bestowed in 2016, came with the blessing of both Russian and American colleagues who had worked together on element 118’s creation through experiments done at JINR.

But agreeing on the existence of new elements, along with their names, has not always been a walk in the woods. In the Cold War years, American and Russian scientists competed to create elements with atomic numbers greater than uranium, the heaviest naturally-occurring element. Tempers, careers and reputations rose and fell by the discovery, confirmation and naming of new substances in the periodic table.

The scramble for priority continued until 1989 – when things changed. A collaboration began between the team from the Flerov Laboratory at Dubna, and an American team working at Lawrence Livermore National Laboratory (LLNL) in California. And that partnership yielded discovery of the superheavy elements 114 and 116 by 1998, and in the next 20 years, the confirmation of elements 113, 115, 117 and 118.

So how and why did collaboration eventually prevail over competition? Did a changing political climate in the Soviet Union thaw scientific relations? Who brokered a conversation and when? Did leadership styles or team dynamics help overcome institutional and political barriers? And if the partnership had never begun, would we still be looking at a periodic table with gaps?

The nucleus: heart of the matter

“I would say it was scientific motivation that enabled the formation of the collaboration – we were interested in the same science, and continue to be so today,” says Mark Stoyer, who now leads the Experimental Nuclear Physics Group at LLNL. He joined the American team in 1998, and says the search for new elements was actually a secondary concern. “It was the desire to understand very heavy nuclei at a more fundamental level. In order to understand the interactions of neutrons and protons with each other in a nucleus, and why a nucleus stays bound together, it is important to study a wide range of nuclei from very light to very heavy systems.”

The nucleus gives an atom its identity. Hydrogen is element number 1. It sits at the top left of the periodic table, the simplest atom with a single positively-charged proton at its heart, and a single negatively-charged electron orbiting around. Next is helium. It has two protons in its nucleus – giving it an atomic number of two and defining it as helium – plus two neutrons. In orbit are two electrons.

It seems simple – and in many ways it is. As the number of protons in the nucleus increases, you move through lithium (3), beryllium, (4) boron (5), and get to carbon (6). If you keep going, you’ll arrive at glowing neon (10), semi-conducting silicon (14), precious silver (47), slippery mercury (80), radioactive polonium (84). Each has an extra proton in a nucleus of increasing mass – along with extra neutrons and orbiting electrons – and all are part of a natural pattern.

But move to the lower right-hand corner of the periodic table, beyond uranium (92), and the elements no longer exist in nature. During the 1940s and 50s, scientists at the University of California, Berkeley bombarded different samples of metals using a particle accelerator, producing neptunium (93), plutonium (94), americium (95), curium (96), berkelium (97), californium (98), and mendelevium (101). They also discovered einsteinium (99), and fermium (100) in the fallout from hydrogen bomb explosions. The team included the pioneering chemist Glenn Seaborg, and physicist Edwin McMillan, who shared the Nobel Prize for Chemistry. Nobelium (102) proved more controversial. A group in Stockholm announced its discovery in 1957 but couldn’t confirm the feat. Seaborg’s group claimed discovery by a different method. The Russian team led by Georgy Flerov came onto the heavy element scene, disputed the American finding, and claimed its discovery themselves.

More disputes followed. During the 1960s and 70s both Russia and America announced they had found what would eventually be called lawrencium (103), rutherfordium (104), dubnium (105), and seaborgium (106). Priority took many years to untangle, in a chilly Cold War atmosphere between the two superpowers. During the early 1980s, another player entered the game. Scientists at the GSI Helmholtz Centre for Heavy Ion Research in Darmstadt, Germany, added bohrium (107), meitnerium (108) and hassium (109) to the roster. Chemistry journalist Kit Chapman, who has a particular interest in the superheavy elements comments, “It’s all or nothing. If you discover an element you are immortalised forever. There is no coming second.”

Yet despite the competition, scientific conversations did continue. “In science, collaboration has existed since the Middle Ages,” says Oganessian, in excellent English. “If I make a discovery, my collaborator will take it into account in his experiment. There are also mistakes to take into account.”

“I attended a seminar in which a Russian delegation was visiting and sharing their research,” recalls Mark Stoyer of the mid-1980s. “The delegation had 3 or 4 members – including Flerov and Oganessian, I believe. The seminar was delivered in Russian, for accuracy, and then translated to English. I remember it vividly because it was a long, slow process for the speaker to say a few things, get it interpreted, then the folks in the audience to ask clarifying questions, have that interpreted, and so on.”

It’s a reminder that despite prevailing difficulties, a common scientific interest still helped bind the parties together.

Cold war thaw

It is no surprise that post-war research into heavy elements should first have emerged in the two nations who completed atomic bomb projects. Expertise in handling radioactive uranium and plutonium gave both a head start. There was also the remarkable parallel experiences of the teams’ leaders.

Georgy Flerov (below, with the young Oganessian) served in the Russian air force during the Second World War. He noticed that work on nuclear fission had ceased to appear in American, British and German journals – and deduced that it had become classified research as the different powers worked towards atomic weapons. As the result of a letter Flerov wrote to Stalin in 1942, the Soviet bomb project began.

Meanwhile in the United States, Glenn Seaborg’s discovery of plutonium, with its fission chain reaction, fed into the Manhattan Project and the atomic bomb dropped by the Allies on Nagasaki in 1945.

“These two men Seaborg and Flerov were more or less the same age,” comments Oganessian. “When they were young, Seaborg discovered plutonium and Flerov discovered spontaneous fission. When the war started, both were involved in atomic bomb projects in their own countries.” After the war, they built their own research teams, working separately in Dubna and at the University of California, Berkeley. “But what is interesting is that with all the discoveries made, sometimes the difference was only a few months,” he added. Russian researchers would publish in Soviet journals, while others’ work appeared in the international press. They were two different worlds.

Work continued on building the particle accelerators required to do heavy-ion science. Seaborg had used a 150cm cyclotron to synthesize elemental discoveries. At JINR, Flerov constructed a 300cm heavy-ion cyclotron. These machines had been invented in the 1930s at Berkeley, and used magnetic fields to whirl charged particles to enormous speeds.

Andrey Popeko (below, in Flerov’s former office at Dubna), deputy director of the Flerov Laboratory, explains the cyclotrons’ role: “At the start of the 1950s, a method of amalgamation of heavy nuclei was devised simultaneously, here and at Berkeley.” By smashing two kinds of atoms together, you could fuse their nuclei to make a heavier one. In this way, a cyclotron lets you produce fermium (100) from uranium (92) by amalgamating it with oxygen (8), creating a nucleus with 100 protons. Andrey goes on, “Both nuclei are positively charged, so they repel each other. You have to accelerate them at the correct energy so the nuclei fuse and don’t disintegrate.”

Seaborg and his team had discovered elements 94 to 101. The goal of the Flerov lab, when it began work in earnest in 1956, was to start by making element 102. As the atomic number went up, however, the chance of making the nucleus decreased, while the requirement for more intense accelerator beams increased. It was definitely tricky science.

By the 1980s the need for more resources was clear in both countries. Mark Stoyer says: “Experiments in the superheavy element region were getting much more difficult and resource-intensive in terms of time, money and materials. The LLNL heavy element group was having difficulty obtaining beam time for experiments at the Lawrence Berkeley Laboratory (LBL) cyclotron. LBL had 3 or 4 groups demanding beam time for their research, and it was a user facility, so the chances of getting even several weeks of time was minimal. In addition, the LBL heavy element group was interested in different kinds of experiments.”

Practicalities were also biting in the last years of the Soviet Union, where investment faltered. Mikhail Itkis (below, at dinner with Oganessian), another former director of the Flerov Lab explained: “When the Soviet Union collapsed there were difficult times. We didn’t have money to buy good detectors and so on. People supported us in principle, but our budget was very poor at that time.”

Despite these issues, the Flerov lab was still a major player in the search for new elements. And as Itkis explains, specialisms helped lay the groundwork for a collaboration. “We have the best accelerator around the world in this field. It’s not high energy, it’s not very low energy for ions, it occupies a special place.”

LLNL at the time had particularly advanced electronics for analysis, while Oak Ridge National Laboratory in Tennessee had good material for the targets used in experiments. It was the basis for a collaboration that continues today. “Each group has success in different areas – so when they come together, there is success, because they are the first in their fields,” says Itkis.

“The first visits to Dubna to perform experiments were to the Soviet Union,” says Mark Stoyer – but times were changing. The Berlin Wall fell in November 1989, and the Soviet Union collapsed in December 1991. “The scientific collaboration started and later flourished during this politically unstable time,” he adds. Team members Ken Moody and Ron Lougheed were in Dubna when Georgy Flerov died in November 1990. By this time Yuri Oganessian was the lab’s director.

Deeper layers

The breakthrough in the search for superheavy elements was first a theoretical one. In the early part of the 20^th century, theoretical physicists worked on the basis that the nucleus of an atom behaved like a drop of liquid, becoming more unstable as the charge increased and disintegrating through the process called nuclear fission.

“The general conclusion for the liquid drop model was that elements higher than uranium may not exist,” explains Oganessian. “This was the limit – and my work started from this limit in 1955. Everybody accepted it and we called it the classical theory of fission. But it was not correct.”

A spanner in the works of the classical theory was that two apparently identical nuclei may decay with different probabilities. Researchers eventually concluded that there were different states in which the nucleus could exist, known as the ground state and the isomeric state. “If you find such a phenomenon that seems to contradict the liquid drop model, this is like Pandora’s Box, you know, it’s opened and then there are so many questions. You come to the new unknown vault and now you have to work to understand it,” says Oganessian.

The idea that the orbiting electrons can exist in a number of energy levels had been known for decades. But within the nucleus itself, scientists realised, there is also structure. Particular numbers of protons and neutrons, corresponding to full shells, are especially stable. In 1949 Maria Goeppert Mayer and Hans Jensen developed this model and shared in the Nobel Prize for Physics.

Glenn Seaborg took this idea further in the late 1960s, predicting that among the superheavy elements there would be what he called an “island of stability” that would make some elements longer-lived than expected. Element 114, for example, should be particularly long-lived if scientists could make atoms with a total of 298 neutrons and protons in their nucleus.

Fascinatingly, Georgy Flerov had also proposed such an idea in 1957 in front of a key Soviet scientific council. Andrey Popeko explains: “Flerov had a very surprising sense of intuition. He could predict many things without detailed study. In 1957, when invited to explain the laboratory’s future work, he presented ten proposals. Among them was the superheavy elements and he explained that somewhere in this region there must be – although he did not call it this at the time – an island of increased stability.”

But to create elements on the way to 114 needed a new scientific technique, which Oganessian pioneered in the 1970s. “Element 106 you may produce from californium and oxygen or by taking lead and using chromium,” says Oganessian – reactions in which a light element is fired at a heavier one. “But after that I proposed a new reaction, called cold fusion.” In this kind of reaction, the two nuclei to be fused together are much closer together on the periodic table, more similar in size. Teams in the US, Russia, Germany and Japan were now all on the experimental trail. Different groups eventually used the cold fusion reaction to create elements 107 to 113 in minuscule amounts.

Even this method, however, met its match. Oganessian recalls, “To produce three atoms of element 113, it took our colleague Kosuke Morita nine years overall, in Japan. So this is one reason why you come to the end of the cold fusion method. It is not practical.”

Oganessian’s new method, which would eventually take the discoveries right up to element 118, was hot fusion. Kit Chapman explains: “In hot fusion, you smash together light projectile nuclei and heavy target nuclei to create a new nucleus. The problem is that the nucleus has a lot of energy and it wants to blow up.” To avoid this, you use a projectile beam of calcium-48 atoms which have the usual 20 protons in their nucleus, but 28 neutrons. “The beam is very neutron-rich,” says Chapman. “It has 8 extra neutrons which it discharges like ballast, relaxing the state of the nucleus so that it remains stable.”

Brokering a collaboration

So how did the US-Russia collaboration begin? Mark Stoyer’s understanding is that the collaboration was brokered by Ken Hulet – who had worked with Glenn Seaborg at Berkeley, and was by now a senior member of the LLNL team – in conjunction with Georgy Flerov from Dubna. The two met in 1989 at one of the regular round of international conferences, and agreed to work together. “This was remarkable at the time,” comments Stoyer. “One of the US nuclear weapons labs and one of the Russian nuclear science labs collaborating – during the Cold War.”

Yuri Oganessian plots a slightly different route into the partnership. He met with Glenn Seaborg to discuss working together on creating atoms of element 106 with particularly high numbers of neutrons in their nuclei. His idea was that this could lead to creating element 114 in a longer-lived, more stable state.

Seaborg was a generation older than Oganessian and they had what the latter describes as a ‘perfect’ relationship. Yet despite the mutual respect, Seaborg did not take up the opportunity – rather it was Oganessian’s contemporary Ken Hulet who agreed to collaborate.

According to another report of the collaboration’s genesis, Ken Hulet made contact with Dubna and agreed a mutually beneficial sharing of resource in terms of detector technology and accelerator capacity. A further account has Oganessian persuading LLNL physicists to share rare kinds of calcium and plutonium for a joint experiment to make element 114.

However the agreement was reached, the collaboration flourished. For his part, Oganessian recalls, “When I became director [of the Flerov Laboratory], I wanted to change the relationship between the two groups that were working for many years on the superheavy elements. 1989 was ithe beginning of Gorbachev time. I guess my vision was quite naïve but I felt, now, I have to try.”

By late 1998, the two groups were preparing to try to make element 114 using a plutonium target and the beam of calcium-48. “The reaction had been tried before but the Dubna/LLNL collaboration had improved the apparatus enough to have much higher sensitivity. All of this improved the quality of the results that then came from the collaboration and fuelled its future success,” explained Mark Stoyer, who joined the group at this point. His wife, Nancy Stoyer, was already on the project.

“The experiment would take 3-4 months, so we divided into two teams to visit Dubna a month apart,” he recalls. No one expected any big outcome at this point, “but amazingly, the first event occurred between our visits,” he says. The partners had successfully produced element 114, and they would soon do the same with element 116.

Leadership and team culture

Further successes followed with elements 115, 117 and 118 – indeed, the Russia-US partnership has been very successful for nearly 30 years, and has its face firmly set to the future. Sergey Dmitriev, the current director of the Flerov Laboratory, will unveil a new accelerator in the next few months (above). “It is called the superheavy element factory,” he says. “The projectile beam of this cyclotron will be at least ten times more intense than we have today. So we can start the synthesis of elements 119 and 120.”

Plans are to make element 119 by using a berkelium (97) target plus a neutron-rich titanium (22) projectile, which has 50 protons and neutrons in its nucleus. In the case of element 120 it will be target made from californium (98). In addition, “We also have a big program to study the chemical properties of the new elements,” says Dmitriev. Such short lifetimes don’t give long to study these elements – but he is confident it’s enough.

The work will still be firmly collaborative. “Several factors are important in sustaining the collaboration,” says Mark Stoyer. “Continued interest and passion in the science, strong working relationships we have developed, and mutual respect. The successes of the past naturally lead to new questions and directions in the field – and we remarkably shared a common vision for the scientific path forward during this time.”

Yuri Oganessian doesn’t mind calling the collaboration idealistic. “We come together and say, ‘you’ve got this, we’ve got that’. Nothing is guaranteed, but all the people who are with you understand. We are all trying together – there is a kind of connectivity that I like very much. The principle is that you contribute as much as you can.”

The cultures of the two groups are significantly different, Stoyer says. “There is a stronger hierarchy in Russia and team members are more focused on their particular task. In the US, all members of the team analyse the data depending on their interest in a particular experiment. In Russia the analysis of the data is performed by a single specialist. The cultures of Russia and the US are very different. In Russia, if it is not strictly allowed, then it is assumed to be forbidden. In the US, if it isn’t strictly forbidden, then it is assumed to be allowed.”

The trust between the partners has been carefully built, however. Mikhail Itkis explains: “It’s very important that in each discovery of a new element, the experimental decay chain is simultaneously analysed in Dubna and in Livermore. Independently. And then after that we compare, and publish.”

Face-to-face meetings are good, reports Oganessian, but online links are crucial. “We have a connection so that every day everyone can see what has happened here.”

Stoyer agrees, “We had a dynamic of vigorous discussion about the interpretation of the data and results from day one. Nothing was ever published without a consensus. We always wanted to produce the highest quality results and valued the working environment that embraced new ideas and their open exchange and critique.”

Without the collaboration, both sides agree the discoveries of the heaviest elements could not have been achieved. Oganessian says, “I would say for sure, without the collaboration, we ourselves here would not have been able to make these elements. The teams in Livermore and Oak Ridge also could not make the elements. There were many barriers, not only political, so we had to ask ourselves, is there a way of combining into a joint group?”

On the two sides of the collaboration, leadership has been handled differently. “Group leadership at LLNL has rotated more than at Dubna and technical leadership has changed more often in the US also,” explains Stoyer.

But while all have contributed to the collaboration’s success, perhaps Yuri Oganessian gives us a good model of what it takes to pursue this esoteric yet intriguing and appealing branch of science, year after year, in the town built on the banks of the Volga.

As Kit Chapman explains, “Oganessian is really the glue in the whole collaboration. He is the driving force – the diplomat that such a project needs. He is a more successful and modern leader than Flerov was, with a collaborative spirit. He is the guy that found the path, who made a way to do what they needed to do.”

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