Would a solid neutron mass be stable?

not asking about neutron stars, where gravity holds neutrons together, rather would the strong force hold individual neutrons together in a solid mass, preventing their decay if one could somehow put them together in a lab?

so in reality you would have to have some sort of energy to feed the neutrons? would neutrons multiply if energy was present or would the basically destroyed under high pressure. does it need a nucleus?

The strong force won't bind two neutrons, much less a mole of them. So the whole question depends on a counterfactual. Hard to answer. However, I don't see what would make a box of unstable particles suddenly stable.

so it would make a bomb of energy eventually? or would it do nothing if only neutrons where present considering that a neutron is a binder of energy.

I don't know what feeding a neutron is. If you can't put two of them together what can be said about a box of them?

Aamikeyy92 said:

so it would make a bomb of energy eventually? or would it do nothing if only neutrons where present considering that a neutron is a binder of energy.

No, and what do you mean by a "binder of energy" ? Gluons ? Good luck getting them to let go. Anyways, Neutrons decompose into Hydrogen atoms, not quarks.

##n_1## - ie: lone neutrons - have a half-life of about 10 minutes ; ##n_2## is a transient state : they aren't really bound, just chillin' together ; ##n_3##, not a thing ; ##n_4## might be possible, but hasn't been reliably observed, yet.

Neutronium - ##n_1## - is a gas.

It wouldn't make a really good bomb, even if you could get all those free neutrons to stay in the same place at the same time. While the bonding ##2H_1 \Rightarrow H_2## releases roughly 3x the heat as lighting an equal mass of Hydrogen gas on fire, it would be over a period of 15 minutes or so, so not that impressive : most likely just raise the temperature of the gas by like 15C or so. Oh, and of course you actually end up with less volume of gas than when you started. So, a total lack of classical "bomb" effect.

Void the hell out of your geiger counter warranty, though.

Suggested reading - Wikipedia : Neutronium

hmmm27 said:

No, and what do you mean by a "binder of energy" ? Gluons ? Good luck getting them to let go. Anyways, Neutrons decompose into Hydrogen atoms, not quarks.

##n_1## - ie: lone neutrons - have a half-life of about 10 minutes ; ##n_2## is a transient state : they aren't really bound, just chillin' together ; ##n_3##, not a thing ; ##n_4## might be possible, but hasn't been reliably observed, yet.

Neutronium - ##n_1## - is a gas.

It wouldn't make a really good bomb, even if you could get all those free neutrons to stay in the same place at the same time. While the bonding ##2H_1 \Rightarrow H_2## releases roughly 3x the heat as lighting an equal mass of Hydrogen gas on fire, it would be over a period of 15 minutes or so, so not that impressive : most likely just raise the temperature of the gas by like 15C or so. Oh, and of course you actually end up with less volume of gas than when you started. So, a total lack of classical "bomb" effect.

Er, no.
Binding energy of two hydrogen atoms is 4,74 eV.
Beta decay of two neutrons does take 15 minutes, but over these minutes it would release 1564 keV. Actually, there is a better alternative. One neutron does decay (782 keV, though some of that energy goes to neutrino not heat), the other is captured and gives a deuteron (2230 keV, heat this time). Or even better, three neutrons... will form a triton. Around 9 MeV between the three.
In thin neutron gas, this is where it should end. H-4 is unbound. t decays, but that takes 12 years, while neutrons run out in 10 minutes.

When a neutron star is torn apart in a kilonova, precisely how much of the energy comes from the kinetic energy of the neutron star, how much from the decay afterwards? You should be able to resolve the two processes by timescale! A neutron star is around 10 km across and falls in the other neutron star at the final speed of the order of 100 000 km/s, giving timescale 100 μs for the tearing apart... and then the beta decay timescale is rather longer. The shortest lived technically relevant beta emitters are the delayed neutron emitters and their half-lives start from hundreds of ms (and go up to tens of seconds).
We´ve seen one kilonova, back in 2017, and we missed it. There was 1700 milliseconds missed after the last gravity waves seen and the first gamma rays, and then 11 hours missed after the last gamma rays seen and first light.
So what would we see if we get a proper full view of the next kilonova? Millisecond to millisecond tracking of full spectrum over hours - nuclear prompt gamma spectrum, nuclear delayed gamma spectrum (isomers/IT), inner electron x-rays, outer electron optical?

We know that there are no nuclei with mass number over 244 and lifetime over 100 million years, because if there were, at least a tiny amount of them should have formed in kilonovas and reached Earth, and we have searched.
But we don´t know where neutron dripline is beyond oxygen. (What fixes dripline would be confirming two consecutive isotopes as unbound scattering states - as with O-25 and O-26).
And how about the quantitative results of kilonova? Like, how much of the lanthanides formed by r-process form directly on the first time, how much by neutron-induced fission of heavy nuclei in the first minutes that free neutrons are around, how much by spontaneous fission? We here on Earth laboratories are limited to proton-rich isotopes of heavy actinides and transactinides, of which Db-268 has half-life 16 hours. Would spectrum of first hours of a kilonova show transactinides, and if yes then how much compared to actinides?

snorkack said:

Er, no.
Binding energy of two hydrogen atoms is 4,74 eV.
Beta decay of two neutrons does take 15 minutes, but over these minutes it would release 1564 keV. Actually, there is a better alternative. One neutron does decay (782 keV, though some of that energy goes to neutrino not heat), the other is captured and gives a deuteron (2230 keV, heat this time). Or even better, three neutrons... will form a triton. Around 9 MeV between the three.
In thin neutron gas, this is where it should end. H-4 is unbound. t decays, but that takes 12 years, while neutrons run out in 10 minutes.

Oh, okay, so bomb. (As you can probably tell, I had neutrons going straight to protium, mostly ignored other decay products, and was using J/mol chemistry figures).

Question : are neutrons actually individually stable (ie: no decay) in a nucleus ? or do they and protons just "morph" back and forth as the day goes on.

hmmm27 said:

are neutrons actually individually stable (ie: no decay) in a nucleus ?

Yes, within the limits of talking about stability of individual parts of a system.

hmmm27 said:

or do they and protons just "morph" back and forth as the day goes on.

No, definitely not.

mfb said:

No, definitely not.

I am not actually so sure.
Ammonia has a low but nonzero barrier for umbrella inversion. Mind you, since ammonia has 3 identic protium atoms, the result of inverting the ammonia molecule is the same as the result of rotating the ammonia molecule. Yet the umbrella inversion is a process to which a specific rate can be assigned. And it is a process through a tunnel - the forbidden/virtual state of flat ammonia, for which there is not enough energy.

How about the process
p+n=n+π⁺+n=n+p? Like in a deuteron? Can the energy barrier and the rate of the Yukawa interchange through the virtual pion be estimated, like the energy barrier and rate of ammonia umbrella inversion can?

I don't see how ammonia would be relevant in any way here,

snorkack said:

How about the process
p+n=n+π++n=n+p?

That's not what OP asked about.

mfb said:

snorkack said:

How about the process
p+n=n+π++n=n+p? Like in a deuteron? Can the energy barrier and the rate of the Yukawa interchange through the virtual pion be estimated, like the energy barrier and rate of ammonia umbrella inversion can?

I don't see how ammonia would be relevant in any way here,That's not what OP asked about.

The OP's question concerned whether a bunch of neutrons could be stabilized in the lab (ie: not neutron-star level pressure/gravity) ; my sidetrack concerned whether individual nucleons shifted between protonic and neutronic states in situ.

mfb said:

I don't see how ammonia would be relevant in any way here,

Might help clean up!

Vanadium 50 said:

Might help clean up!

This is a question of interpretation of quantum mechanics. If we observe a deuteron having one neutron and one proton now, and we know that the deuteron also had one neutron and one proton a second ago, and 10 milliards of years ago, because the deuteron is stable, how do we know whether it is the "same" neutron all along, or whether any process has interchanged the neutron and proton natures? I suggested a parallel with ammonia. Three protons, which are indistinguishable fermions. How do we know whether the three protons in ammonia molecule ever interchange positions?

snorkack said:

how do we know whether it is the "same" neutron all along, or whether any process has interchanged the neutron and proton natures?

That's not a question with a meaningful answer, but more importantly it is not the question OP asked.