午夜福利1000集合

You鈥檙e the only person alive to have an element named after them. How does it feel to join the likes of Albert Einstein and Marie Curie?

For me, it is an honour. The discovery of element 118 was by scientists at the Joint Institute for Nuclear Research in Russia and at the Lawrence Livermore National Laboratory in the US, and it was my colleagues who proposed the name oganesson. My children and grandchildren have been living in the US for decades, but my daughter wrote to me to say that she did not sleep the night she heard because she was crying. My grandchildren, like all young people, reacted quite calmly.

How many elements have you helped discover since you started working on them in 1956?

We鈥檝e come a long way. When I started, we had only 101 elements. Today, it鈥檚 118, completing the seventh row of the periodic table. Since I joined the , I鈥檝e mostly been making elements, which is why I helped discover many of them. Our collaboration with US researchers has also been strong, even during the cold war.

How do you make superheavy new elements?

With great difficulty. For an atom to exist, it needs a nucleus that balances attractive and repulsive forces, so we need a 鈥渕agic number鈥� of protons and neutrons. We create new elements by accelerating atoms to a tenth of the speed of light and smashing them into heavier, target elements. When we get a collision, there鈥檚 a small chance they鈥檒l fuse to make a superheavy nucleus. Then there鈥檚 the challenge of cooling it down and shepherding the element into a detector.

What other challenges do you face?

As atoms get bigger, they need a higher proportion of neutrons to protons, so to create a superheavy element, the atoms you smash together need an excess of neutrons, too. The problem for us is getting the raw materials. We鈥檝e been using calcium-48, which is very rare and expensive. One gram costs more than $200,000. Making the target material is also slow: our US collaborators produced just 22 milligrams of target material 鈥� berkelium, element 97 鈥� after one year of neutron bombardment in a nuclear reactor.

How long do superheavy elements last for?

The longest-lived synthesised isotope of element 112 has a half-life of 29 seconds. For element 114 it鈥檚 2.6 seconds, and element 116 is about 60 milliseconds. 118 lasts for around 0.9 milliseconds, so they are getting increasingly unstable. And as superheavy atoms get bigger, they get harder to make. For element 118, we currently produce just one atom per month.

How much higher will the

There has to be a limit, and I think it will come from relativistic effects. When the positive charge of the nucleus increases, the velocity of the electrons increases too, bringing them closer to the speed of light. We are already close. For example, the innermost electrons of element 112 travel at seven-tenths of light speed. Bringing the velocity of the outermost electrons even closer to light speed may change an atom鈥檚 chemical properties, breaking periodicity.

Oganesson should, in theory, be a noble gas. Do you think it will behave like one?

That will be the first task when we study element 118鈥檚 chemical properties in earnest. It is very unlikely to be a noble gas, which would mean the end of periodicity as we know it 鈥� a very big deal. Our big challenge now is to work out how to handle element 118 when it has a half-life of less than 1 millisecond.

We want to explore the chemical properties of our most recent superheavy elements, and especially their periodicity. To do that, we need to produce more of them. We are involved with a joint proposal to create a new facility. We call it the Superheavy Element Factory. Our US colleagues will improve their reactor to produce more target material, while here in Dubna we will build a new accelerator and new experimental machine. We aim to have a first beam at the new accelerator by the end of this year and to increase production by a factor of 100. These steps may also be key to making elements beyond 118 for the first time.

Why are superheavy elements important?

For me, it is about tackling fundamental questions in atomic physics, but it also bears on astrophysics. Look at a neutron star. It may be 20 kilometres across, yet be the same mass as the sun. They are made of very dense neutron matter: if you cut 2 kilometres into one, you would find material with the same density as an atomic nucleus. It is some sort of soup of neutrons, fewer protons and very heavy neutron-rich nuclei.

鈥淚t looks like the end of the material world, but I don鈥檛 think it is鈥�

What are you looking forward to now?

To see closer to the top of the 鈥�island of stability鈥�. Theorists predict that there should be some superheavy atoms, with certain combinations of protons and neutrons, that are extremely stable. We have a 鈥渃ontinent鈥� of stable elements that ends with lead, element 82. As we go heavier than lead, we have a 鈥減eninsula鈥� created by the likes of thorium and uranium, which are radioactive and so decay over time into lighter elements. Superheavy nuclei are highly charged matter. The repulsion of positively charged protons prevents the formation of large nuclei and this moves us into the deep water of the 鈥渟ea of instability鈥�, where elements break down ever faster. It looks like the end of the material world, but I don鈥檛 think it is.

The island of stability is a controversial idea. You think it could exist?

If it didn鈥檛, we could not synthesise elements heavier than element 112. Their lifetimes are extremely small, but if neutrons are added to the nuclei of these atoms, their lifetime grows. Adding eight neutrons to the heaviest known isotopes of elements 110, 111, 112 and even 113 increases their lifetime by around 100,000 times. This is because we are heading inland on the island of stability and I feel we are now on firm ground, but we are still far from the top of the island where atoms may have lifetimes of perhaps millions of years. We will need new machines to reach it.

This article appeared in print under the headline 鈥淏reaking the periodic table鈥�