New type of nuclear fission discovered
December 6, 2010 by Lin Edwards
The experimental apparatus with which Otto Hahn and Fritz Strassmann discovered nuclear fission in 1938. Image: Wikipedia.
(PhysOrg.com) -- Nuclear fission, or the splitting of a heavy nucleus, usually results in symmetrical fragments of the same mass. Physicists attribute the few known examples of fission that is asymmetric to the formation in the resultant fragments of "magic" nuclei, which are extremely stable nuclei with all energy levels filled. Now, experiments at the European particle physics laboratory at the Organization for Nuclear Research (CERN) near Geneva in Switzerland have found the isotope mercury-180 splits asymmetrically into ruthenium-100 and krypton-80 rather than the expected zirconium-90.
The nucleus of mercury-180 contains 80 protons and 100 neutrons, and symmetrical fission would result in two nuclei of zirconium-90, which contains 40 protons and 50 neutrons. This result was expected to be dominant especially because 50 and 40 are magic and semi-magic numbers respectively, meaning the levels in the nucleus would be completely filled with protons/neutrons.
Andrei Andreyev, of the University of the West of Scotland in Paisley, and colleagues carried out the experiments at the ISOLDE facilities at CERN. These facilities enable physicists to work with pure beams of highly unstable heavy elements and collect their reaction products and analyze them. They began with a beam of the highly unstable thallium-180, which has 81 protons and 99 neutrons, and which decayed primarily by the capture of an electron to convert one of the protons into a neutron, giving the 80 protons and 100 neutrons of mercury-180. This should then theoretically split symmetrically.
Instead, the mercury isotope split into ruthenium-100, with 44 protons and 56 neutrons, and krypton-80, with 36 protons and 44 neutrons. These are isotopes with incompletely filled energy levels.
Asymmetric splitting has been seen previously in isotopes of uranium, which often split into the isotope tin-132 and a smaller fragment. The tin-132 has all energy levels in the nucleus filled, with 50 protons and 82 neutrons, and is an extremely stable isotope. This asymmetric fission was therefore easy to explain, but the new findings cannot be explained in this way, and this is the first time such unexplainable fission has been observed.
The researchers then analyzed the energy requirements for different types of mercury-180 splitting, and found less energy was required for the asymmetric split found experimentally than for the symmetrical split predicted by the theory. Team member Piet Van Duppen of the Catholic University of Leuven in Belgium, said this may mean other isotopes in the same area of the periodic table may also split into asymmetric daughter fragments. Another isotope of mercury has now been tested, and it also split asymmetrically.
The results of the experiments highlight the gap in the scientific knowledge of nuclear fission, which still cannot be fully described in detail some seven decades after the process was discovered. The gap may be filled in as new radioactive beam facilities become available in the next few years, including the Facility for Antiproton and Ion Research in Germany and the Facility for Rare Isotope Beams in the US.
The experimental results of the experiments are published in Physical Review Letters.
More information: New type of asymmetric fission in proton-rich nuclei, Physical Review Letters, A. N. Andreyev et al. Accepted for publication.
© 2010 PhysOrg.com
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Dec 06, 2010
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Dec 06, 2010
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Dec 06, 2010
Rank: 3.9 / 5 (12)
Simply being systematic and diligent would have required this. It's just fundamental basic research, for bob's sake. I wonder what other obvious things we have missed so far.
Dec 06, 2010
Rank: 1.3 / 5 (13)
The above research offers no particular scientific gain in terms of problem importance though it does generate publications. But people need publications to keep jobs so they lobby for funds in research--I wonder what new areas of research had their funding crowded out by Facilities for Antiproton and Ion Research and t Rare Isotope Beams?
Dec 06, 2010
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http://tambourine...ect.html
Dec 06, 2010
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Uh, isn't Alpha-emission considered 'fission' ??
Dec 06, 2010
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Dec 06, 2010
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With thousands of possible isotopes to review, this isn't simple, fast or cheap.
Dec 06, 2010
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Dec 06, 2010
Rank: 4.1 / 5 (11)
I fail to see how increasing our understanding of fundamental particle behavior will be anything but a boon to those other areas of research you mentioned. But I digress... antigravity research currently needs funding? Really? There's so much we don't even know about the non-anti one, and it's so much easier to test.
Dec 06, 2010
Rank: 5 / 5 (12)
We've had to live with a "semi-empirical" nuclear mass formula for several decades, maybe soon we'll finally arrive at a fully empirical model - and with it, a powerful new understanding of nuclear chemistry.
It's difficult to anticipate how that knowledge will impact our society with any precision at this point, but it's a step toward achieving a new level of mastery over nuclear transmutations that could impact everything from the impending energy crisis, to medical applications, to long-range spaceflight capabilities.
Dec 06, 2010
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Dec 06, 2010
Rank: 1.3 / 5 (13)
So they discovered some of the secrets of alchemy. The alchemists knew the use of what they have, but never bothered to give it a scientific label as this group did and does.
They simply used the innovations. Powerfully so. It just goes to show you that it may take modern 'science' to label something, but it only takes a smart man with original thinking ad primitive tools in order to get to what we even today, would call 'astounding science'.
Dec 06, 2010
Rank: 5 / 5 (14)
Dec 06, 2010
Rank: 5 / 5 (4)
Good point: IIRC, there's some work, not yet repeated, that suggests there may be 'higher order' effects...
http://technology...p1=Blogs
quote:
Roentgenium-111 shouldn't exist on Earth. Now a group of nuclear physicists claims to have found an ultra-stable version of it in gold.
...
It's fair to say that his claim to have found element 122 in thorium is disputed and not yet entirely accepted by the majority of his colleagues.
...
The discovery of roentgenium in gold is almost certain to trigger a similar response. So it'll be interesting to see now whether anybody can repeat this result.
/quote.
Dec 06, 2010
Rank: 4.7 / 5 (14)
KBK - Did you read the article? Do you know what an accelerator is? We have been creating gold and other types of elemental transformations for decades now. The idea that this is something that people in laboratories could have done hundreds of years ago is ludicrous.
Dec 06, 2010
Rank: 4.6 / 5 (8)
The theorists discover something about the world, then the engineers build something useful with it. Welcome to reality, it's a team effort, which first requires information. These guys get the information. Until you've built something with it, get to work.
Dec 06, 2010
Rank: 1.2 / 5 (9)
http://www.scienc...0u19.htm
No particle, revealed in accelerators had ever some practical usage during last seventy years, so it's probable, it will not get usage during next fifty years. The devices like PET scanners, MRI are independent to collider research. The world became too poor to even reproduce some historical achievments, like the managed flight to Moon. We simply have no money to sponsor blind collider research, which is remnant of cold war era.
Dec 06, 2010
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Dec 06, 2010
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Has anyone done a study of the progress of partical physic and which discoveries could have been made decades before they actually occured if time and money had been directed corrctly.
For instance the big bang inflation theory could have happened decades before it did. The radiation from the big bang could have been discovered years before it had if someone had build a detector for it.
Dec 06, 2010
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Dec 06, 2010
Rank: 5 / 5 (8)
Accelerators aren't like telescopes, there is no "time" on a collider. We run the collider for as long as we have money, and any scientist working on the project gets to look at the data generated. The 'media savy' scientists probably just have more money for more grad students ;)
Dec 06, 2010
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Dec 07, 2010
Rank: 1.7 / 5 (6)
Although X-rays were discovered through a natural mechanism.
Dec 07, 2010
Rank: 5 / 5 (2)
This is wrong. Fission of U-233, U-235 and Pu-239, the major isotopes suitable as nuclear fuel, results in two unequal fission products.
http://upload.wik...ield.svg
Dec 07, 2010
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Dec 07, 2010
Rank: 3.7 / 5 (12)
Not quite. The particle was theoretically predicted by Dirac (or at least it came out of the Dirac equation) and was confirmed by observing cosmic rays with a cloud chamber.
Dec 07, 2010
Rank: 5 / 5 (2)
Ethelred
Dec 07, 2010
Rank: 5 / 5 (5)
You are quite right, my mistake. Anderson did use a cloud chamber in 33.
I don't consider the theoretical discovery to be the discovery. If that was the case then we would already be saying we had discovered the Higgs Boson. Dirac also thought it was the proton at first that would be the positive electron, Oppenheimer had to discourage him to get the real theory out of him.
Dec 07, 2010
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Dec 07, 2010
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Essentially, most of the low-hanging fruit from electromagnetism, mechanics, and early quantum mechanics has been plucked. Until more 'pure' science is known we can't progress to the challenging engineering topics you wish we could make.
Dec 07, 2010
Rank: 4 / 5 (1)
Is 4 seconds considered "extremely stable" in this instance, or is that a typo?
Dec 08, 2010
Rank: 2 / 5 (1)
And calling this stuff 'stable' seems weird to me also.
http://www.ptable.com/
Ohh there is a neat video on this site for tin.
http://www.chemic...tin.html
A block metallic tin with 'tin pest' it looks like some bizarre disease as the block expands, fractures, and turn gray.
Ethelred
Dec 08, 2010
Rank: 1 / 5 (9)
Why these ideas & theories aren't considered? Because it would A) render the whole mainstream physics incompetent B) most of theorist would lose their jobs immediately. This stance of mainstream physics is so apparent, their most influential proponents are even not trying to hide it.
Dec 08, 2010
Rank: 1 / 5 (9)
"Just suppose.. that some smart aleck came up with a simple self-evident, closed theory of everything. I---and so many others---have had a perfectly wonderful life pursuing the will-o'-the-wisp of unification. I have dreamed of my children, their children and their children's children all having this same beautiful experience.
All that would end.
APS membership would drop precipitously. Fellow members, could we afford this catastrophe? We must prepare a crisis-management plan for this eventuality, however remote. First we must voice a hearty denial. Then we should ostracize the culprit and hold up for years any publication by the use of our well-practiced referees. Just to be safe, we should put the paper on our Index---I mean in our index--- where it can be lost for centuries..."
Dec 08, 2010
Rank: 5 / 5 (6)
In both cases neither Sockpuppet showed the slightest sign of know Dr. Wilson was telling a joke.
The post seems to based on one by AKT a few days earlier here:
http://www.techre...v/25376/
And ZephirAWT was on the thread. And AKT said this about the AWITSBS site the Zephyr pushed
So I guess that AKT is not engaging in another Zephyr fake discussion. Though it does some to be two guys Cranking away.
AKT also seems to unclear on the concept of humor.
Ethelred
Dec 08, 2010
Rank: 1 / 5 (8)
Dec 08, 2010
Rank: 5 / 5 (10)
Dec 08, 2010
Rank: 5 / 5 (8)
First assume a spherical chicken of uniform density.
Ethelred
Dec 08, 2010
Rank: 5 / 5 (7)
Professor Wilson was also rather vigorously attacked for subverting the process to have that quotation added to the journal. Perhaps you should actually learn about the snippets of quotation that you spew upon every physics forum once you've been rated on the crackpot scale.
Dec 08, 2010
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Dec 08, 2010
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http://users.navi...arce.txt
Dec 08, 2010
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Dec 08, 2010
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So in all these years not ONE person has let slip the truth? In all these years we definitively knew of a more unified field of physics, and not ONE person in a moment of egotism used that unified physics to win themselves a nobel prize? To solve some deep unresolved issue of science? Balderdash. Complete nonsense the things you're supposing.
Science is slow. Sorry. It is. It takes time to gather evidence to support claims. It takes thousands of scientists, postdocs, grad students year-round work for years on end to come up with even tiny advances anymore. The simple days of a lone scientist discovering something significant are gone.
Dec 08, 2010
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Ethelred
Dec 08, 2010
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Dec 08, 2010
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I posit that it is you, and others like you, who are the truly dogmatic. So convinced are you of your beliefs in a secretive world of scientists that you will buy into any exotic theory so long as it damages the reputation of scientists. You are the one who will refuse to hear evidence to the contrary of your favored theories. Before you point out the speck in your neighbor's eye, perhaps consider removing the log from your own.
Dec 08, 2010
Rank: 1 / 5 (10)
This problem with theorists is therefore not so theoretical at all, as recent Wilson memo indicates clearly: the theorists will ignore existence of more general theory obstinately, if it could threat their existence at least a bit. The similarity with medieval approach of Holy Church is apparent here: the physicists became real enemies of further evolution of understanding.
Dec 08, 2010
Rank: 1 / 5 (9)
http://www.americ...ritarian
http://www.guardi...-science
Why experts are usually wrong? Because they're trained to think in biased, i.e. specialized way.
http://www.nypost...QJHmT5QO
Is "publish or perish" biasing science toward gradualism?
http://arstechnic...ence.ars
The corruption of science?
http://news.bbc.c...0481.stm
We Must Stop the Avalanche of Low-Quality Research The main cause: the growth in the number of researchers.
http://chronicle....f/65890/
Scientists, you are fallible. Get off the pedestal and join the common herd
http://www.guardi...question
Dec 08, 2010
Rank: 5 / 5 (10)
Dec 08, 2010
Rank: 5 / 5 (10)
Dec 08, 2010
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Dec 08, 2010
Rank: 1 / 5 (9)
When the speed of energy spreading isn't sufficient anymore inside of condensing cluster of molecules, the so-called spontaneous symmetry breaking occurs: a new space-time gradients will emerge under formation of newly created droplets of new phase.
We can observe, when the speed of scientific method isn't sufficient to follow the speed of society evolution, new theories are starting to emerge (condense) outside of mainstream. These droplets are still sparse and separated, but they could merge into continuous phase anytime. I'm working on it purposefully with gradual reconciliation of existing theories with simple unifying principle.
Dec 08, 2010
Rank: 5 / 5 (11)
Similarly, Planck quantized black body radiation, which was later described by Quantum Mechanics, which will probably receive an upgraded explanation in the future. We're by no means done learning.
As for dense aether I think you've already said why it can't work ;) Explain why the observer has a special role in the universe. Explain how that special role in the universe works. You've just made a series of unfounded presumptions and followed them to their illogical conclusion.
Dec 08, 2010
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Dec 08, 2010
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Dec 08, 2010
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2) No, the Schwarzchild metric is a solution for a single, non-rotating spherical body of uniform density. It has absolutely nothing to do with outside bodies. In fact it's well known that outside bodies can only be treated as perturbations to the single barycenter object.
3) my following statements were the "proof." You explicitly postulate that the observer is a special role in the universe without any backing evidence. it's an unfounded postulate with no alternative support.
Dec 08, 2010
Rank: 5 / 5 (7)
Prove it exists.
Dec 08, 2010
Rank: 5 / 5 (8)
You're confusing the meanings associated with Observer and Observable. Observable merely means the set of space-time events that fall within the past light cone of some other event in space-time. There need not be an observer there at all.
There is no justification behind the claim that the conscious/rational observer occupies a 'special' role in the universe.
Dec 08, 2010
Rank: 5 / 5 (8)
Finally: string theorists are free to postulate strings all they'd like. Until they produce some evidence, I have no reason to believe in their existence. Unlike the big bang postulation which has a wealth of evidence to support its existence.
Dec 09, 2010
Rank: 5 / 5 (6)
Oh boy, where to start with this?
Existense of phlogiston is postulate of phlogiston theory. Does that convince you to believe in phlogiston? How about if I say the ghost postulate is the basis of my ghost theory, so you must believe it? Yes, postulates are ultimate truths within the context of the theory they underpin. That does not mean they are true at all with regards to reality.
Dec 10, 2010
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Dec 10, 2010
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Dec 11, 2010
Rank: 5 / 5 (5)
The world is made up of the four elements of fire, water, earth and air. Aristotle said so and that makes all research useless and without purpose.
When will people understand that pure science research is how we begin to understand our world and the posibilities we have to use it to our advantage without destroying it?
Dec 11, 2010
Rank: 1.3 / 5 (4)
Dec 11, 2010
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Dec 11, 2010
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Dec 11, 2010
Rank: 3.3 / 5 (3)
We could easily deal with food problems if more people actually worked in farming and production jobs instead of working in the false economy stock market and other paperwork jobs.
We have plenty of fertile land in the U.S. that has hardly even been touched.
Additionally, we could be far more productive if a higher number of farms would convert to greenhouses or hydro/aeroponics whenever and where ever possible.
Dec 13, 2010
Rank: 5 / 5 (1)
I would like to comment on a few of the previous posts.
Indeed, asymmetric fission, i.e. the process of a mother nucleus undergoing fission resulting in two nuclei with different mass, is a common phenomenon when one of the fission products is characterized by nuclear magicity. As an example, heavy elements (like 236U) split asymmetrically. But in those cases one of the fragments is lying in the vicinity of 132Sn, which is a doubly magic nucleus. For elements lighter than uranium the influence of the structure of 132Sn is less pronounced and the fission occurs symmetrically.
The term ‘magicity’ reflects here the complete filling of nuclear orbitals by protons and/or neutrons. This does not mean (e.g. 132Sn) that the resulting nucleus is stable against beta decay, but it has other features, like a strong binding energy of the nucleons.
Dec 13, 2010
Rank: 5 / 5 (1)
Indeed, asymmetric fission, i.e. the process of a mother nucleus undergoing fission resulting in two nuclei with different mass, is a common phenomenon when one of the fission products is characterized by nuclear magicity. As an example, heavy elements (like 236U) split asymmetrically. But in those cases one of the fragments is lying in the vicinity of 132Sn, which is a doubly magic nucleus. For elements lighter than uranium the influence of the structure of 132Sn is less pronounced and the fission occurs symmetrically.
The term ‘magicity’ reflects here the complete filling of nuclear orbitals by protons and/or neutrons. This does not mean (e.g. 132Sn) that the resulting nucleus is stable against beta decay, but it has other features, like a strong binding energy of the nucleons.
Dec 13, 2010
Rank: 5 / 5 (5)
Indeed, asymmetric fission, i.e. the process of a mother nucleus undergoing fission resulting in two nuclei with different mass, is a common phenomenon when one of the fission products is characterized by nuclear magicity. As an example, heavy elements (like 236U) split asymmetrically. But in those cases one of the fragments is lying in the vicinity of 132Sn, which is a doubly magic nucleus. For elements lighter than uranium the influence of the structure of 132Sn is less pronounced and the fission occurs symmetrically.
The term ‘magicity’ reflects here the complete filling of nuclear orbitals by protons and/or neutrons. This does not mean (e.g. 132Sn) that the resulting nucleus is stable against beta decay, but it has other features, like a strong binding energy of the nucleons.
Dec 13, 2010
Rank: 5 / 5 (6)
The reason why this is only discovered now, lies in the very exotic nature of 180Hg. It is far away from the valley of stable nuclei, and the production cross section is low. It is also very short-lived, so it is necessary to guide the nuclei to the experimental set-up in a very short time.
Posted by Nick Bree, co-author
Dec 13, 2010
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Ethelred
Dec 13, 2010
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Dec 13, 2010
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Posted by Jan Diriken (co-author)
Dec 13, 2010
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Dec 13, 2010
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Posted by Jan Diriken (co-author)
Dec 13, 2010
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Dec 14, 2010
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