What is the most accurate way to represent the heavy nucleus of an element?

[JaredJames]

Well now Jarid

Ooh, bad choice. Exceptionally bad choice.

 

[Drakkith]

Well now Jarid, i had no idea this forum was such a serious place. Thats really good to know!

John.

Then you are missing the entire purpose of the forum. To educate people on the current views of science. You wouldn't go to a Ford Truck Fan forum and be allowed to stay if you were constantly bashing Fords. That isn't what the forum is for! It is for people that like Ford Trucks!

Also, even if it this wasn't a serious forum, your defense of your picture was pretty serious...

 

[edguy99]

No, don't get me wrong. I think the standard model is great. I'm just suggesting that the visual representation of heavy nucleus's could be drawn in a way to better represent the properties we observe in experiments.

Critically, in heavy elements, using Iron as an example, we don't observe anything to suggests that Iron-52, with 26 protons and 26 neutrons, has 52 little individual bits stuck together by the strong force. What we do observe is a heavy nucleus, that physically gets bigger roughly by the cube of its mass. And with all the various fission, fusion, isotopes, and decay modes, we observe a nucleus that displays properties much closer to two bundles stuck together by the strong force. That's a bundle of protons and a bundle of neutrons, separate, but stuck together by the strong force.

I drew this image as a better representation of the properties we observe;

That image shows a Carbon, Iron and a Uranium nucleus. Below each image is an Isotope of each element with more neutrons than protons. So i displayed the neutrons in the isotope as being just a bit larger than the proton bundle. This image is physically a better representation of the properties we observe in heavy elements than the image with the single bundle of dots suggesting Iron-52 has 52 separate little bits stuck together.

John.

To me your pictures strongly represent a couple of important features of the nucleus, but also tend to misrepresent other features.

Good: right away it represents weight vs size very visually and I think it also gives the idea of about the same number (or more) of neutrons then protons.

Not good: for small numbers of neutrons and protons (less then 20) the size rule (relative to cube of mass) is not correct.

Not good: it seems to imply some sort of "compartment" for the protons and neutrons being separated that way, in fact the strong force applies to each proton and neutron individually and mixing them together (as the picture in the 1st post) more strongly suggests that in a visual way.

Currently, the only other style that does not seem to evoke too many complaints is the Lewis style of atoms, you often see the nucleus (protons and neutrons and non-valence electrons) as one circle (53 picometers for hydrogen, larger for other atoms). The various circles are shown bound with dots representing the valence electrons.

 

[John37309]

Thank you edguy99 for some constructive scientific criticism, much appreciated!

Good: right away it represents weight vs size very visually and I think it also gives the idea of about the same number (or more) of neutrons then protons

Thanks, that's one of the points i was trying to make. When discussing isotopes in a visual sense, this type of image has benefits. This type of image can also be adapted to more easily explain various decay modes for the nucleus.

Not good: for small numbers of neutrons and protons (less then 20) the size rule (relative to cube of mass) is not correct.

I didn't actually spend time getting the exact scale correct. It was just a quick image to discuss the topic.

Not good: it seems to imply some sort of "compartment" for the protons and neutrons being separated that way, in fact the strong force applies to each proton and neutron individually and mixing them together (as the picture in the 1st post) more strongly suggests that in a visual way.

Yea, maybe. I would disagree with you though. That compartmentalisation is also implied from the big cluster image of the nucleus. The cluster image implies that none of the protons mix together in any way. Same with the neutrons. But in reality, there is no evidence to suggest that in a heavy nucleus, the protons stay separate from each other. Or that the neutrons stay separate from each other. There is evidence to suggest that the wave functions mix together kinda like electron orbital hybridisation.

Currently, the only other style that does not seem to evoke too many complaints is the Lewis style of atoms, you often see the nucleus (protons and neutrons and non-valence electrons) as one circle (53 picometers for hydrogen, larger for other atoms). The various circles are shown bound with dots representing the valence electrons.

Now that's a really good point. Let's take the Lewis structures as an example. Lewis structures have nothing what-so-ever to do with reality. But they are a really great way to explain what's happening with molecules in chemistry. So i guess that's really the point I'm making here. My type of drawing can be good for explaining some things, but not others.

Thanks for the feedback edguy99,
John.

 

[Drakkith]

Yea, maybe. I would disagree with you though. That compartmentalisation is also implied from the big cluster image of the nucleus. The cluster image implies that none of the protons mix together in any way. Same with the neutrons. But in reality, there is no evidence to suggest that in a heavy nucleus, the protons stay separate from each other. Or that the neutrons stay separate from each other. There is evidence to suggest that the wave functions mix together kinda like electron orbital hybridisation.

What do you mean no evidence? I could have swore the like charges of electrons greatly affect their orbitals, and similarly the like charges of protons greatly affect their positions or orbitals in the nucleus.

Now that's a really good point. Let's take the Lewis structures as an example. Lewis structures have nothing what-so-ever to do with reality. But they are a really great way to explain what's happening with molecules in chemistry. So i guess that's really the point I'm making here. My type of drawing can be good for explaining some things, but not others.

Thanks for the feedback edguy99,
John.

The fact that your drawing can be good at certain things was never in question. I think it is fine depending on who your target audience is and what it is trying to explain.

 

[BruceW]

I just made a picture to represent the Woods-Saxon potential, which gives an empirical potential describing the nucleus. The basic idea is that the deeper the potential, the more likely the nucleons are to be there. The potential is deepest in the middle of the nucleus, (where its whiter), so nucleons are more likely to be in the centre.
This is probably the most scientifically accurate picture of the nucleus I have heard of. Hopefully the picture uploads correctly.

 

[John37309]

I just made a picture to represent the Woods-Saxon potential, which gives an empirical potential describing the nucleus. The basic idea is that the deeper the potential, the more likely the nucleons are to be there. The potential is deepest in the middle of the nucleus, (where its whiter), so nucleons are more likely to be in the centre.
This is probably the most scientifically accurate picture of the nucleus I have heard of. Hopefully the picture uploads correctly.

Bruce,
It kinda looks like the way people are currently drawing the electron, kinda like a cloud, as opposed to a solid particle that is orbiting at high speed. I would give that image quite high merit. I like the line of thought that suggests atoms, electrons, and even the quarks inside them are just wavy energy clouds. I like it!

John.

 

[BruceW]

Thanks, I guess the difficulty is that you can either describe the potential of the nucleus in general, or talk about what each particle is doing individually, but it's not easy to draw a picture which explains both of them..

 

[John37309]

Thanks, I guess the difficulty is that you can either describe the potential of the nucleus in general, or talk about what each particle is doing individually, but it's not easy to draw a picture which explains both of them..

Yep, that's very true Bruce! Its a good picture, it does explain many properties of a nucleus!

There are billions of Iron atoms in an iron bar you buy in your hardware store. But its looks and acts like an Iron bar, it has the properties of an Iron bar, so we draw it as an Iron bar.

John.

 

[danR]

Bruce,
It kinda looks like the way people are currently drawing the electron, kinda like a cloud, as opposed to a solid particle that is orbiting at high speed. I would give that image quite high merit. I like the line of thought that suggests atoms, electrons, and even the quarks inside them are just wavy energy clouds. I like it!

John.

I suspect this is a picture of a potential, a probability, of where a nucleon may be found, rather than a picture or depiction of what a nucleus looks like.

Regarding the electron cloud-pictures: they are not intended to imply that electrons have cloud-like or 'wavy' structure (they may, who knows, but that's not what they are intended to show); the shading indicates the degree of probability that an electron may be somewhere, or other.

 

[danR]

I hope you don't take some of the comments that have been presented too harshly, but the way (pictorially and verbally) you are presenting your theory is extremely common. And very baffling to unravel for experts. I don't mean your theory itself. I mean the way you explain it. They see this sort of presentation hundreds, even thousands of times, and each time they have to go through the same wearisome steps to understand it, explain why it is probably inaccurate, and too often explain that it doesn't really mean anything all.

So people get frustrated.

 

[John37309]

Dan,
i do like a good scientific debate, its productive. I'm not put off at all by peoples comments. If everyone patted you on the back for great suggestions, then science would be no fun.

John.

 

[edguy99]

... When discussing isotopes in a visual sense, this type of image has benefits. This type of image can also be adapted to more easily explain various decay modes for the nucleus.

I like this one, as it more properly models the binding forces and conveys the idea of coupled protons and neutrons (they don't contribute to spin). Basically these are layers of protons (blue) separated by neutron layers (grey). The only rule is you must have an insulating neutron between any two protons and the proton starts at the top (http://www.animatedphysics.com/element_spin.jpg" ).

 

[danR]

Dan,
i do like a good scientific debate, its productive. I'm not put off at all by peoples comments. If everyone patted you on the back for great suggestions, then science would be no fun.

John.

It's best to leave the debating part of science theory to specialists. I was in a science for liberal arts course at the university here, and often, because I have a very curious and active mind, would talk a lot, and question and dispute things. The prof had a mixed blessing: a non-major that actually had keen interest in physics, but often had too much to say, and too little knowledge.

It is also almost certainly true that the past century has never seen any fundamental physics contribution from an intelligent layperson. You only have to type "nucleus" "nucleon" into Google scholar, and look at the sheer mountain of very imposing documents, papers, dissertations. It's not like you're in the deep end of the pool, you're in the Mariana trench. If people will excuse me for this small Google sample from some 110,000 entries:

Coupling effects in the elastic scattering of the exotic nucleus 6He on protons
[PDF] from cea.frV Lapoux, N Alamanos, F Auger, Y Blumenfeld… - Physics Letters B, 2001 - Elsevier

... Nucleus–nucleon elastic scattering can be described using the complex microscopic
JLM potential [6] which only depends on the scattering energy and on the neutron
and proton densities of the nucleus. The potential is deduced ...
Cited by 45 - Related articles - Get at CISTI - All 17 versions

Nucleon-nucleus optical-model parameters, A> 40, E< 50 MeV
FD Becchetti Jr… - Physical Review, 1969 - APS
Proton-nucleus and neutron-nucleus standard optical-model parameters are given that
represent, quite well, much of the elastic scattering data in the range A>40, E<50 MeV. These
parameters were determined by fitting simultaneously a large sample of the available ...
Cited by 951 - Related articles - All 4 versions

Projectile Fragmentation of the Extremely Neutron-Rich Nucleus^{11} Li at 0.79 GeV/nucleon
T Kobayashi, O Yamakawa, K Omata… - Physical Review Letters, 1988 - APS
Projectile fragmentations of 11 Li, 8 He, and 6 He have been measured at 0.79
GeV/nucleon. Production cross sections and momentum distributions of the produced isotopes
(Z≥2) are measured inclusively. Transverse-momentum distributions of 9 Li from the ...
Cited by 343 - Related articles - All 5 versions

Gluon production in current-nucleus and nucleon-nucleus collisions in a quasi-classical approximation* 1
[PDF] from arxiv.orgYV Kovchegov… - Nuclear Physics B, 1998 - Elsevier
We calculate gluon production in deep inelastic scattering of the current off a large nucleus and
in nucleon-nucleus collisions. In a covariant gauge calculation the transverse momentum spectrum
of the gluon is determined by the final state interactions of the gluon with the nucleons in ...
Cited by 329 - Related articles - Get at CISTI - All 6 versions

Dirac-Equation Impulse Approximation for Intermediate-Energy Nucleon-Nucleus Scattering
BC Clark, S Hama, RL Mercer, L Ray… - Physical Review Letters, 1983 - APS
In this application of Dirac phenomenology a relativistic impulse approximation is used to describe
proton-nucleus elastic scattering at intermediate energies. The results demonstrate the superiority
of this relativistic treatment over the nonrelativistic impulse approximation, especially with ...
Cited by 271 - Related articles - All 4 versions

 

[SpectraCat]

I like this one, as it more properly models the binding forces and conveys the idea of coupled protons and neutrons (they don't contribute to spin). Basically these are layers of protons (blue) separated by neutron layers (grey). The only rule is you must have an insulating neutron between any two protons and the proton starts at the top (http://www.animatedphysics.com/element_spin.jpg" ).

I don't think it explains all that much ... it is just intended to help understand the microstates arising from spin coupling. For example, why aren't the spins of the lower two neutrons in lithium-7 paired? I also don't understand what you mean by "more properly models the binding forces".

 

[edguy99]

I don't think it explains all that much ... it is just intended to help understand the microstates arising from spin coupling. For example, why aren't the spins of the lower two neutrons in lithium-7 paired? I also don't understand what you mean by "more properly models the binding forces".

They don't have a proton line between them. Do you use any visual image in your mind to remember nuclear spin?

I mean by "more properly models the binding forces" that it helps you remember for instance that Helium4 is very tightly bound whereas other isotopes are less well bound - bond strength for one proton and one neutron (Hydrogen2) is about 1.1 MeV, Helium4 bond strength is almost 30 MeV (over 7 MeV per nucleon).

 

[SpectraCat]

They don't have a proton line between them. Do you use any visual image in your mind to remember nuclear spin?

No, I don't think that has anything to do with it. I think they are unpaired because they are fermions in degenerate energy levels, according to the nuclear shell model. The usual rules for populating such states is to put one fermion in each degenerate state before pairing any of them .. this is because there is an energy penalty associated with pairing them. This is definitely how electrons are added to atomic and molecular states (Hund's rule of maximum multiplicity), however I am not certain that this is the case for nucleons.

I mean by "more properly models the binding forces" that it helps you remember for instance that Helium4 is very tightly bound whereas other isotopes are less well bound - bond strength for one proton and one neutron (Hydrogen2) is about 1.1 MeV, Helium4 bond strength is almost 30 MeV (over 7 MeV per nucleon).

Right, but that has more to do with the shell model than the spin-pairing. Helium is so much more stable because it has a completely filled shell for both protons and neutrons.