Friday, July 24, 2009

Copernicium and the Island of Heavy Nuclei

The Heavy Ion Society (Gesellschaft für Schwerionenforschung, GSI) in Darmstadt, Germany, has dedicated its mission to slamming together heavy nuclei to produce even heavier nuclei.

For that purpose they use UNILAC, the 120-meter long Universal Linear Accelerator which accelerates ions to 20 percent of the speed of light to smash them on lead targets, and SHIP, the Separator for Heavy Ion reaction Products, an electromagnetic separator and detector assembly which is used to analyse the reaction products.

During the last decades, the GSI has thus become known with their discovery of new chemical elements in the periodic table. The latest one, element 112, has now been named "Copernicium," after astronomer Nicolaus Copernicus.

Previous ones were named Bohrium (element 107, named after Niels Bohr), Hassium (element 108, after the Latin name for the state Hesse, where GSI is located), Meitnerium (element 109, after Lise Meitner), Darmstadtium (element 110, after the city Darmstadt), and Roentgenium (element 111, after Wilhem Röntgen). These elements have a half-life ranging from seconds to minutes.

The element 112 (112-277) has been produced for the first time in fusion reactions of zinc-70 (with proton number 30) projectiles with lead-208 (proton number 82) targets. In a three weeks' experiment which ran 24 hours per day, one nucleus of element 112 was first observed on February 9, 1996. The nucleus disintegrates in a series of α-decays, which allows its identification:



The half-life of the new element Copernicium is not yet clear due to lacking statistics. But the discovery could be reproduced in other laboratories in Russia and Japan. Here is a photo of the proud discoverers (Credits: A. Zschau, GSI):



Sigurd Hofmann, the leader of the SHIP group at GSI, has given a talk about these dicoveries at the American Chemical Society meeting in San Diego, in 2001, to which you can listen here.

Besides the fun it brings to slam together heavy things, these experiments have the scientific purpose of better understanding the structure of elementary matter. Eventually, you know, physicsts want to derive all chemistry from QCD, but we're far away from that. The heavy ion beams produced at the GSI have also been used since 1997 for cancer treatment.

One theory that has been around for several decades is that at sufficiently high number of protons and neutrons the stability of elements will increase dramatically. In the periodic system, this patch has been dubbed the (conjectured) "Island of Heavy Nuclei." Its position shifted a bit with new models for nuclear structure, but it's still believed to be there, somewhere above atomic number 120.

I've always found this intriguing. Imagine, once we've crossed the valley of short-lived elements, we could produce some elements stable enough to form molecules and create chemical reactions that aren't taking place by natural processes anywhere in the known universe. Granted, serious nuclear physicists don't believe they would be that stable, but likely undergo spontaneous fission. But still, it would make for a nice science-fiction scenario, wouldn't it? A completely new kind of chemistry.




The New Element 112.
Zeitschrift für Physik A 354, 229-230 (1996), DOI 10.1007/BF02769517.

8 comments:

Uncle Al said...

96-Curium-247 with a 15.6 million year half-life, (W-Z)/Z = 1.573 is a richer target than 82-lead-208, (W-Z)/Z = 1.537. The island of stability tremendously packs in neutrons.

It is usually quicker to start at the end.

Georg said...

"Eventually, you know, physicsts want to derive all chemistry from QCD, but we're far away from that."

Grin :=)
1st, what do You want to improve by
introducing "chromo"?
2nd, what about Thermodynamics?
3rd, what about a more than qualitative
theory for liquid state?
Chemistry is rather well founded on
Quantum Theory and Thermodynamics,
although this is only qualitative
for most "Chemistry", Chemists feel fine with it.
Regards
Georg

Phil Warnell said...

Hi Stefan,

I think this is all a conspiracy funded by those that print periodic tables to have it become necessary to buy new ones :-) More seriously my congratulations go out to the research team and I’m happy to see Copernicus be honoured, although I’m not certain of the connection since this has to do with inner space rather than the outer variety having been his prime concern. It’s also intriguing as you point out that if this island of stability exists one day we may create elements that just don’t exist in nature; just as we have already been able to manage with temperature create conditions that don’t otherwise exist; well at least not yet. This has me mindful of those science fiction stories where the space craft of some alien visitor is found to be made from an element unknown to us. With this report of yours it may be us earthlings one day may represent being the little green men for others:-)

Best,

Phil

Neil' said...

One of the weirdest ideas in trans-uranic progression is about pair-production and elements at or above Z = 137. There is also the problem of the "proton drip line" which I just heard about. See e.g. http://en.wikipedia.org/wiki/Element_137. Some propose calling E137 "Feynmanium" since he talked about the weird implications. (BTW, it isn't the classical/simple-Bohr problem of electrons in 137 literally going FTL, it is the more modern interpretation about energy issues etc.)

Bee said...

Hi George,

I think you missed the point of that remark, it was aimed at our recent discussion of the question What is Fundamental?. The question isn't whether QCD is useful or even necessary to do nuclear physics (in the sense of accurate descriptions and predictions) but whether or not it's in principle possible to arrive at it from the underlying theory. Today, nuclear physics consists of a couple of more or less well working models (much like heavy ion physics does), but the relation of those to the underlying theory is present, at best, by motivation and inspiration rather than derivation. Best,

B.

stefan said...

Hi Phil,

This has me mindful of those science fiction stories where the space craft of some alien visitor is found to be made from an element unknown to us.

actually, Sabine and I had discussed a similar point, and that finding some of these elements somewhere in space would be a strong hint at alien advanced civilizations...


Hi Neil

One of the weirdest ideas in trans-uranic progression is about pair-production and elements at or above Z = 137

indeed, but the actual critical atomic number will be higher as nuclei are not point charges.

By concidence, this week's PRL has on its cover an illustration from a calculation of the collision of uranium nuclei, collisions ... also used to produce super-strong electric fields by the huge number of interacting protons to test spontaneous positron-electron pair emission predicted by the quantum electrodynamics theory (arXiv:0904.3047v3).

Cheers, Stefan

Phil Warnell said...
This comment has been removed by the author.
Phil Warnell said...

Hi Stefan & Bee,

Yes that would be certainly an interesting discovery. For me I’ve always been fascinated by the fact that elements we are already aquatinted with required a star to go supernova before they themselves existed. You might then call these emergent elements and to the same extent you could call these new ones; yet only in this case they required the emergence of intelligence before they could exist.

Many see emergence as an aspect of coincidence, while I see it as a consequence of potential. I would also contend this forms the dividing line between the theorists, where some see reality as forming from numerous options, of which ours represents as being only one; while others feel underlying potential(s) may form to limit what it can be. I have then always found it strange, that while many would resist being limited by destiny; they would never want their potential to be.

Best,

Phil