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Author Topic: Is the inside of the nucleus hot?  (Read 3987 times)

Offline McKay

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Is the inside of the nucleus hot?
« on: 29/06/2014 23:05:03 »
Is the nucleus [of an atom] hot? That is - is there vibration and motion going on? The gluons, quarks and the hadrons as whole are moving, vibrating?
If so, could the nucleus, in principle, be cooled down and what would happen to it - disintegrate?
« Last Edit: 30/06/2014 21:12:45 by McKay »


 

Offline jccc

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Re: Is the nucleus hot?
« Reply #1 on: 30/06/2014 00:19:01 »
The nucleus is not hotter than its surrounding.

The heat/energy is stored within nucleus force field. During nucleus reaction, the force field rearranged so release some of the stored energy/heat which is a lot because near the nucleus, strong force field holds a lot energy/enertron. During chemical reaction, only nucleus outer force field rearranged by new electrons positions so release much less energy/enertron.

No matter how cold it is, nucleus will not disintegrate. It will if hot enough.

I am not QM believer. So...
 

Offline alancalverd

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Re: Is the nucleus hot?
« Reply #2 on: 30/06/2014 07:54:55 »
No. Heat is a property of an ensemble of particles that can transfer kinetic energy to other particles.
 

Offline evan_au

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Re: Is the nucleus hot?
« Reply #3 on: 30/06/2014 17:41:13 »
As I understand it, the average kinetic energy of a group of atoms is related to the temperature of the substance. This is not kinetic energy of the center of mass of the atoms, but kinetic energy measured relative to the center of mass. More kinetic energy->higher temperature.

Since most of the mass of an atom (and hence, most of the kinetic energy) is held in the nucleus, I suggest that the motion of each nucleus is a good indicator of the temperature of the substance as a whole.

It is possible for a group of particles at one temperature to interact with a set of particles at a different temperture. Due to thermodynamics, there will be a transfer of momentum from the high-temperature particles into the low-temperature particles, tending to equalise their temperatures.

One example would be in the moderator of a uranium-fueled nuclear reactor, where the high-energy neutrons emitted by the fission process collide with the nuclei of the moderator. The moderator heats up, while the neutrons, after many colisions have reduced their energy significantly, becoming "thermal" neutrons which can trigger further nuclear fission reactions.

The two "daughter" nuclei recoil at high velocity, representing a high temperature. They then collide with moderator, collant and casing to transfer their energy to the reactor as a whole.

Another example may be in the LHC, where bunches of protons (Hydrogen nuclei) are accelerated to very close to the speed of light. Each bunch has a similar velocity, and may be considered to have a low temperature. However, when two bunches are colided head-on, the relative velocity between the protons (and their constituent quarks) is immense, allowing physicists to study events taking place at temperatures thought to have ocurred in the Big Bang.
 

Offline McKay

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Re: Is the nucleus hot?
« Reply #4 on: 30/06/2014 21:12:27 »
Hmm, ok, but I am not quite satisfied.
Perhaps "hot" is the wrong word. And perhaps I should have said "the inside of the nucleus", instead of just "nucleus". But I think about proton relative to neutron motion within the nucleus. The quark and gluon motion within the nucleus - isn't there energy swirling around inside? Or is the inside of the nucleus completely still?
 

Offline JP

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Re: Is the inside of the nucleus hot?
« Reply #5 on: 30/06/2014 21:38:37 »
Indeed, within the nucleus there is a lot of energy, principally in the binding forces holding protons and neutrons together!  But the problem is that this energy can't be easily removed.  In cooling down traditional matter, you bring a cold object (one whose particles are moving slowly) in contact with a hot object (one whose particles are moving quickly) and because the particles bump into each other (or radiate to each other), they all tend towards the same average energy over time. 

But the particles within the protons and neutrons don't behave this way because the force binding them behaves uniquely: it is very strong at tiny distances and drops off to almost nothing once you're outside the nucleus.  You could get in and interact with these particles if you fire a very high energy particle into a proton or neutron (as they do in high energy particle experiments), but this probably isn't what you mean by cooling...
 

Offline yor_on

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Re: Is the inside of the nucleus hot?
« Reply #6 on: 01/07/2014 06:45:32 »
This one is illuminating, well, if you accept the nomenclature :)

http://news.sciencemag.org/physics/2010/04/mass-common-quark-finally-nailed-down

"Nominally, a proton consists of two up quarks and a down quark that hold themselves together by exchanging gluons. (A neutron consists of two down quarks and an up quark.) In reality, the gluons themselves exchange gluons. And myriad quark-antiquark pairs flit in and out of existence. So the proton is actually a roiling infinity of quarks and gluons in which the three original “valence” quarks, which determine the proton’s identity, make up less than 2% of the mass."

And you can compare it to "In the case of the proton, its mass is roughly 100 times larger than the sum of the masses of the three unpaired quarks that make it a proton (by determining its electric charge and other properties). Describing the other ~99% is where things can get impressionistic."

http://profmattstrassler.com/articles-and-posts/largehadroncolliderfaq/whats-a-proton-anyway/

Just remember that no one I know of actually have been able to look inside to see what is going on :)
==

A better description of quark mass, with links.

http://dispatchesfromturtleisland.blogspot.se/2014/06/up-quark-down-quark-mass-difference.html
« Last Edit: 01/07/2014 07:53:08 by yor_on »
 

Offline evan_au

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Re: Is the inside of the nucleus hot?
« Reply #7 on: 01/07/2014 18:51:18 »
Thermodynamics demands that, over time, all atoms/molecules in a gas will tend towards the same statistical distribution of energies, even if the gas is composed of many different types of particles.

The rules of quantum mechanics means that nucleons are forbidden from all adopting the same energy levels. (Ignoring the not-insignificant problem that we can't uniquely mark each nucleon, let alone later read back these markings so we can determine what energy the particle now has - all without changing the energy level that is being measured!)

There are well-defined rules for the energy levels of electrons around a hydrogen nucleus; other atoms are more complex, but still covered by quantum theory.

However, energy levels inside a nucleus are not well understood at this time. At a high level, there are two major types of particles: protons and neutrons. Protons repel each other electrostatically, while neutrons don't, which causes protons & neutrons to adopt different energy levels. Too many of one or the other, and the nucleus decays into a different type of nucleus. There are a number of theories, which almost predict the results.

At a more detailed level, each proton or neutron consists of 3 quarks, but energetically, they appear to be more stable as a group of 12 quarks, corresponding to a Helium-4 nucleus: 2 protons+2 neutrons.

Given that the particles within a nucleus will take on defined energy levels, about the only statement you can make is whether the nucleus is in the ground state or not. If the nucleus is in an excited state (which means the nucleons have more energy than in the ground state; you could describe this as being "hot"), then the nucleus can decay, for example by emitting a gamma ray. If this decay depends on the weak nuclear force, then the decay can take a considerable amount of time before it happens.
 

Offline McKay

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Re: Is the inside of the nucleus hot?
« Reply #8 on: 02/07/2014 17:48:20 »
Hmm, so, from what evan_au said, radioactive nucleus can be thought as an excited nucleus.. ?
Can the nucleus be excited again by force? Say, if tritium decays in helium-3 via beta emission, can high energy electron be forced in to helium-3 to get back the excited, not stable tritium?
« Last Edit: 02/07/2014 17:50:58 by McKay »
 

Offline evan_au

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Re: Is the inside of the nucleus hot?
« Reply #9 on: 03/07/2014 09:17:26 »
if tritium decays in helium-3 via beta emission, can high energy electron be forced in to helium-3 to get back the excited, not stable tritium?
Beta emission is easily detectable; but what is not detectable is that some of the energy in this decay is carried off by a ghostly neutrino. Unfortunately, neutrinos are very hard to control, so it's far beyond our current technology to simultaneously fire an electron and a neutrino at the same nucleus.

Can the nucleus be excited again by force?
Yes, firing a neutron at Thorium, Uranium or Plutonium will leave the the nucleus in an excited state, which is likely to result in the nucleus splitting into two smaller nuclei. These "daughter nuclei" are also in an excited state, and are in turn likely to decay within a few minutes.

radioactive nucleus can be thought as an excited nucleus..
Some nuclei are still radioactive when that nucleus is in its lowest energy state. This can occur because some other nucleus (or couple of nuclei) have a lower total rest mass than the original nucleus.

Radioactive decay tends to occur in a direction which results in a lower total rest mass for the decay products.
 

Offline jccc

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Re: Is the inside of the nucleus hot?
« Reply #10 on: 17/07/2014 05:14:20 »
Is the nucleus [of an atom] hot? That is - is there vibration and motion going on? The gluons, quarks and the hadrons as whole are moving, vibrating?
If so, could the nucleus, in principle, be cooled down and what would happen to it - disintegrate?

After rethink, I think yes, the nucleus is hot, very hot. It's like the core of the Earth even we don't feel the heat.

Nucleus force field holds the heat, store it as energy. In the force field changed, the atom either absorb or release heat.

When a gas is compressed, gas atoms nucleus force field becomes smaller, therefore release heat. When gas expending, it absorbs heat. The nature uses force to balance/make everything. One attraction force and one repulsion force, and here we are.

How wonderful!
 

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Re: Is the inside of the nucleus hot?
« Reply #10 on: 17/07/2014 05:14:20 »

 

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