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  • Inside this labyrinth of pipes and chambers, superheavy elements are being fused into existence.

  • This machine is part of an international hunt to unlock the mysteries of this new class

  • of elements that typically don't exist here on Earth.

  • Pushing these element discoveries really is pushing into models of how matter is formed

  • in the big bang.

  • How do we model matter?

  • And how do we model the formation of the universe?

  • Superheavy elements exist for a fraction of time and are nearly impossible to catch.

  • But understanding them could force us to reimagine the most iconic scientific symbol of all time:

  • the periodic table.

  • In 1869, Russian chemist, Dmitri Mendeleev, laid the foundations for what would become

  • the modern periodic table.

  • He arranged the known elements in order of increasing atomic weightstarting with the

  • lightest ones with the least protons and working his way up.

  • And as he did so, a curious pattern started to emerge.

  • What happened is he noticed that at regular intervals, chemical properties were repeating

  • themselves.

  • Because of this periodicity in the chemistry, he realized that there were elements at that

  • time that had not yet been discovered but should be there.

  • In the following years, scientists started isolating the elements Mendeleev predicted

  • from various materials.

  • Scandium was found in a hunk of euxenite, gallium in a piece of zinc ore, and hafnium

  • in a zirconium mineral, to name a few.

  • The table's design was revised and perfected as more elements were added.

  • But as nuclei got heavier and heavier, finding them became a bit more complicated.

  • When we refer to heavy elements, we're talking about things that have these very large nuclei

  • that have a lot of protons in them.

  • Above uranium, nothing exists here naturally.

  • They have more protons in their system than anything that we have naturally occurring.

  • In order to continue their quest towards a complete periodic table, scientists couldn't

  • just continue isolating elements from existing materials.

  • They had to create them.

  • So we use what's called a particle accelerator or specifically a cyclotron, which is a large

  • instrument that accelerates ions to a fraction of the speed of light.

  • Cyclotrons have been used to discover heavy elements ranging from curium to plutonium.

  • And most recently, Dr. Shaughnessy's team collaborated with a lab in Russia to complete

  • the periodic table's 7th rowthe home of the superheavies.

  • When we make one of these new elements in the cyclotron we really have to just add up

  • protons.

  • So for instance, if we wanted to look for element 116, we could take something with

  • 20 protons and we can take something with 96 protons, and if we can get those two nuclei

  • to completely fuse together for even a short time that means we have an element 116, one

  • atom of it.

  • These elements are very short lived they're not very stable, so they decay very quickly.

  • Some superheavy elements only exist for just milliseconds.

  • So, in order to confirm they created one, the team had to work backwardssifting

  • through the data to find the signal that told them a heavy element was actually there.

  • The Flerov lab in Dubna has an incredible cyclotron that's really a work horse.

  • And we at Livermore have access to various target materials.

  • So we provided our expertise, the Russians provided their expertise, and together discovered

  • elements 114 through 118.

  • While efforts to discover more elements continue, Dr. Shaughnessy and Dr. Gates have shifted

  • their sights to studying the ones we already have.

  • We know almost nothing about these superheavies, including whether or not we've put them

  • in the right place on the periodic table.

  • Right now, when an element is discovered, we're putting it in the periodic table based

  • on its number, mostly for convenience.

  • But the periodic table, let's remember, it was constructed to be a living document on

  • the chemistry of these elements.

  • The models predict that these heavy elements might behave unexpectedly due to something

  • called relativistic effects.

  • We have these big massive nuclei and what's happening is they're accelerating their electrons

  • to near relativistic speeds.They're going so fast that they're being dominated by the

  • theory of relativity.

  • What that does is it's changing the mass of the electron and that's changing how it bonds

  • and its chemistry.

  • So when we get to this last row of the periodic table, what we see sometimes, is that the

  • chemical properties down a given group may invert or do something totally different.

  • We believe that we have them in the right position, but we also don't think we've proven

  • that.

  • And so, what we did was we built FIONA to actually prove that what we think is true,

  • actually is true.

  • Hooked up to the Lawrence Berkeley National Lab's 88 inch cyclotron, FIONA is one of

  • the newest tools designed to study superheavy elements.

  • Its primary goal is to experimentally confirm their mass numbers.

  • But before FIONA can measure the mass, the team needs to create a superheavy element.

  • So we are in cave one at the Building 88 facility.

  • The beam comes from the cyclotron, which is right through that wall, and then it travels

  • all the way down this line here until it reaches our target out the other side.

  • This is what our targets look like, or this is three fourths of a target.

  • We have just a couple of thousand atoms thick of whatever our target material actually is.

  • What we're interested in is one nucleus from the beam hitting one nucleus from the target

  • and completely fusing.

  • The problem is that doesn't happen very often.

  • Nuclei are very small compared to atoms, so a nucleus is about 10,000 times smaller than

  • the atom itself.

  • When the beam comes in, what it actually sees is mostly empty space. It actually passes through

  • our target, mostly.

  • And then very, very rarely we'll get this head-on collision that makes that atom that

  • we want.

  • Right inside this box, that's where our elements are made.

  • Now our job is to find a way to separate all that junk that we don't want, from that one

  • atom that we do.

  • Everything travels through the Berkeley Gas-Filled Separator - a machine equipped with giant

  • magnets that bend the excess atoms away from the superheavy the team is interested in.

  • Then it enters stage one of FIONA.

  • That's all of that equipment over there.

  • It traps it in a small volume, and then it sends it on to stage two of FIONA.

  • Magnetic fields then send the superheavy atom into a specialized loop.

  • And, it's the specific path it takes within that loop that tells the team its mass.

  • FIONA's first scientific experiment started in June of last year.

  • We were able to confirm that those new heavy elements that we've discovered really do have

  • the number of neutrons and protons that we think that they do.

  • But confirming that isn't quite enough to know for sure that we've put them in the

  • correct place on the tablewe also have to explore their chemistries.

  • We have atoms trapped in a cubic millimeter of volume for a time that we pick.

  • We can add in different gases and we can change the amount of time we trap things for.

  • We can look, "Does this gas react with this atom?

  • And if so, what does it make?

  • We could actually learn quite a bit about the chemistry of these new elements.

  • And at Dr. Shaughnessy's lab, her team is looking into alternative methods.

  • Here at Livermore we're trying to develop a way to do aqueous chemistry of 114.

  • Hopefully this collection of data from both the gas and aqueous phase will start to paint

  • a more complete picture.

  • If we do see some real shift in chemistry we would have to rethink that last row.

  • What does that mean for our periodic table?

  • 150 years after its conception, the periodic table is reaching a turning point.

  • As Dr. Gates, Dr. Shaughnessy, and teams around the world continue to unlock the mysteries

  • at its borders, they're also starting to question just how much further those borders

  • can be pushed.

  • There are people who have tried to predict where the periodic table will end.The most

  • common number thrown about is around element 172, or 173.

  • The issue is that the probability of making the two nuclei come together, it gets smaller

  • and smaller as we go up in element numbers.

  • So with element 118 it was a very small probability that we would make it.

  • Now for 119 and 120 it's even getting lower and lower.

  • In order to push out to heavier elements there's going to have to be some real shifts in technology

  • compared to what we have now.

  • You're trying to answer a basic scientific question.

  • How many elements are there in the universe, and what are their chemical properties?

  • That's something that's interesting, regardless of whether or not there's any scientific applications

  • for it.

  • If you break down an advanced piece of technology, a new medicine, or an energy source to its

  • essential partsyou always end up with the same thing: those same blocks that make

  • up you and me and the stars in the night sky.

  • It's about the elements themselves.

  • The formation of these elements alone tells us a lot about nuclear theory and how the

  • nucleus holds together.

  • We've already changed over the decades how we think of the nucleus.

  • So that's where the application is right now, is really in just our fundamental understanding

  • of the universe.

Inside this labyrinth of pipes and chambers, superheavy elements are being fused into existence.

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周期表の限界に挑む超重原子工場 (This Superheavy Atom Factory Is Pushing the Limits of the Periodic Table)

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    林宜悉 に公開 2021 年 01 月 14 日
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