Unexpected Shape of Lead-208 Nucleus of May Force Scientists to Reevaluate Atomic Nuclei Models (phys.org) 22
"An international research collaboration led by the University of Surrey's Nuclear Physics Group has overturned the long-standing belief that the atomic nucleus of lead-208 is perfectly spherical," reports Phys.org.
They add that the discovery "challenges fundamental assumptions about nuclear structure and has far-reaching implications for our understanding of how the heaviest elements are formed in the universe..." [A] new study published in Physical Review Letters used a high-precision experimental probe to examine its shape and found that rather than being perfectly spherical, the nucleus of lead-208 is slightly elongated, resembling a rugby ball (prolate spheroid)... Using the state-of-the-art GRETINA gamma-ray spectrometer at Argonne National Laboratory in Illinois, U.S., scientists bombarded lead atoms with high-speed particle beams accelerated to 10% of the speed of light — equivalent to circling the Earth every second. The interactions created unique gamma-ray fingerprints of the properties of excited quantum states in lead-208 nuclei — in other words, the nuclei were energized — which, in turn, were used to determine its shape.
Theoretical physicists, including those at the Surrey Nuclear Theory Group, are now re-examining the models used to describe atomic nuclei, as the experiments suggest that nuclear structure is far more complex than previously thought.
They add that the discovery "challenges fundamental assumptions about nuclear structure and has far-reaching implications for our understanding of how the heaviest elements are formed in the universe..." [A] new study published in Physical Review Letters used a high-precision experimental probe to examine its shape and found that rather than being perfectly spherical, the nucleus of lead-208 is slightly elongated, resembling a rugby ball (prolate spheroid)... Using the state-of-the-art GRETINA gamma-ray spectrometer at Argonne National Laboratory in Illinois, U.S., scientists bombarded lead atoms with high-speed particle beams accelerated to 10% of the speed of light — equivalent to circling the Earth every second. The interactions created unique gamma-ray fingerprints of the properties of excited quantum states in lead-208 nuclei — in other words, the nuclei were energized — which, in turn, were used to determine its shape.
Theoretical physicists, including those at the Surrey Nuclear Theory Group, are now re-examining the models used to describe atomic nuclei, as the experiments suggest that nuclear structure is far more complex than previously thought.
resembling a rugby ball? (Score:3, Funny)
So IOW, the soccer rules are out the window and you're allowed to touch the nucleus with your hands?
Re: (Score:3)
Re: resembling a rugby ball? (Score:2)
Worse - imagine kicking a nucleus ball - thatâ(TM)s far more dense. Like - as dense as a neutron star, so youâ(TM)re talking in the region of 8*10^16kg for a rugby ball
Re: (Score:3, Funny)
So IOW, the soccer rules are out the window and you're allowed to touch the nucleus with your hands?
The real question is, can you lick it [memeguy.com]?
Re: (Score:1)
3 licks to the center.
Nuclear models are semi-empiric (Score:4, Informative)
That is, they diverge from one another severely where data isn't available, and converge, despite their vastly different assumptions, where data is available.
It isn't news they are "wrong", we know very well why, it is just that the real shit is so complicated, that it simply does not compute.
The imperfect models will be "refined" to reflect the new data until such time as our "AGI" overlords come up with the real model.
The one that we won't understand anyway.
Or, alternatively, we'll get it, as we've gotten most stuff so far and still be cool.
Re:Nuclear models are semi-empiric (Score:4, Informative)
Bismuth was wrong until we incorporated the relativistic effects of the outer electrons.
This might actually be a great find if it can help rule in/out certain gravity models.
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The relativistic effects on electron orbitals is limited to the increase of apparent electron mass with electron speed. It has nothing to do with gravity.
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What does "perfectly" mean here? Clearly not that. (Score:4, Insightful)
How can anything made out of discrete anything be "perfectly" any shape? If you zoom in far enough on anything, it turns out to be made out of smaller parts, and it's lumpy. And the parts are moving.
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Didn't the epicyclists take measurements that supported their circular-orbit theory within margins of error too?
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Didn't the epicyclists take measurements that supported their circular-orbit theory within margins of error too?
If epicycles aren’t working, you’re not using enough epicycles.
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No. They were adding epicycles because errors accumulated over the error margins continuously and for no valid reason within the theoretical framework. With the electron orbits there is no such thing. Not only do you get an exact solution, which predicts the spectral lines perfectly, it also explains the empirical formulas derived from the observations.
Magic is an illusion, double magic doubly so. (Score:3)
Hm, the headline says that this nucleus is slightly less spherical than expected. I wonder how non-spherical we're talking about, like as a ratio of the "equatorial" diameter to the "polar". The summary doesn't say. Maybe I can piece it together from the article itself. How hard can it be?
"Lead-208 is the heaviest known doubly magic nucleus and its structure is therefore of special interest. Despite this magicity,"
Aaaand I'm out.
Re:Magic is an illusion, double magic doubly so. (Score:4, Informative)
"Lead-208 is the heaviest known doubly magic nucleus and its structure is therefore of special interest. Despite this magicity,"
There are magic numbers [wikipedia.org] of neutrons or protons in the nucleus, which are especially stable: 2, 8, 20, 28, 50, 82, and 126. With 82 protons and 126 neutrons Lead-208 hits two of these, so it's doubly magic.
"Smithers, get the Polaroid." (Score:2)
(For the comedy-impaired, that was comedy; bad comedy.)
God (Score:2)
God might or might not play dice, but fer sure he likes infinite series with no closed form. Also, has quite a sense of humor.