OUR car rolls up to a forbidding pair of metal gates set into a high wall. 鈥淲e have to have a lot of security here because we have a reactor,鈥� says my guide, nuclear physicist .
We are entering the (JINR) in Dubna, Russia, a 3-hour rickety train ride from Moscow. Dubna, once a 鈥渃losed鈥� scientific town dedicated to nuclear research, is now open to visitors. Its claim to fame is as the birthplace of the heaviest, most ephemeral atoms known.
Since 2006, Oganessian has made a clutch of these fragile, superheavy elements (SHEs) at the JINR鈥檚 . Unlike elements such as carbon, oxygen and silver, SHEs are not found in nature, and most of those made so far break down via radioactive decay shortly after forming.
Advertisement
Despite this transience, soon after I leave, researchers from the US will arrive to help Oganessian test the properties of the unnamed element with atomic number 113 (representing the number of protons in its nucleus).
As yet, 113 has not officially joined the periodic table 鈥� a drawn-out process. But scrabbling for this accolade is not Oganessian鈥檚 priority. He is more interested in assigning chemical properties to his elements. Their short lives make this difficult, so why do it?
Certain 鈥渕agic鈥� numbers of protons and neutrons should make some SHEs stable. These will reside in a region of the periodic table known as the 鈥渋sland of stability鈥�. At the pinnacle of the island should be a version, or isotope, of element 114 with 184 neutrons, predicted to have a half-life of aeons. Oganessian鈥檚 113 isostope, with a half-life of milliseconds, lies on the island鈥檚 shores, and a more stable 113 isotope should exist. The stable SHEs might have exotic properties that could be harnessed in new materials, but as none has yet been made, the closest things are their less stable isotopes, like Oganessian鈥檚 113.
鈥淎s no element in the 鈥榠sland of stability鈥� has yet been made, less stable 113 is the closest thing we have鈥�
Sergey Dmitriev, the director of the Flerov lab, shows me to the heart of the facility where the experiments on 113 will happen. In a huge room, we speak against a deafening roar of a cyclotron particle accelerator. Here, charged ions of calcium (atomic number 20) whip round in a vacuum, and are then spat out to collide with berkelium (atomic number 97). This produces 117, which decays to form 113.
Only 30 atoms of 113 are made a year, so the first task of the joint Russian-US team will be to increase the yield. Then, to test the properties of 113, they will rush the rare atoms through a tube and fire them across a sheet of gold (see diagram).
Like other SHEs, 113鈥檚 nucleus is so big and positively charged that it pulls in the outermost electrons much more tightly than in lighter elements. As these electrons are normally the easiest for other atoms to interact with, this should decrease the atom鈥檚 chemical reactivity. Observing how far the atoms travel across the gold surface without binding is a way to measure this reactivity.
Because the reactivity will determine how strongly atoms of this element bind to each other, and therefore how difficult it is to break them apart to form a gas, the distance travelled can be used to deduce 113鈥檚 boiling point. The team will also measure the distance travelled by 113鈥檚 鈥渉omologue鈥� thallium, which sits above it in the periodic table, and by an unreactive noble gas, both of which have known boiling points. The same technique has revealed that Copernicium (element 112), a recent addition to the periodic table, is , and is the only metal known to be a gas at room temperature.
The JINR is also planning an ambitious new building, the 鈥渆lement factory鈥�, that will churn out atoms for testing at a much faster rate. 鈥淭hen you can get big statistics,鈥� says Oganessian.