Neutrons

[lemur]

The only thing I really know about neutrons is that they add to the atomic weight of an element without adding to its charge. I suppose I also know that a star can develop into a neutron star, which would be very dense. Now I am wondering about the following questions:

 

1) are there any natural sources of free neutrons besides radioactive decay?

 

2) why/how to they decay into a proton and an electron after a short time? Are they actually just a weakly (nuclearly) bonded configuration of these two particles?

 

3) why don't they exhibit ideal gas law behavior? I would expect them to behave like a non-combustible form of hydrogen if they were permanently charge-stabilized, but apparently they don't. Is this because they lack the atomic volume that comes with being an atom with electrons orbiting due to electrostatic force?

 

4) Should anti-neutrons, if they are found to exist, be called "old-trons"?

[ydoaPs]

Neutrons are released in fission reactions as well, and you're going to Hell for the old-trons joke.

[swansont]

2) why/how to they decay into a proton and an electron after a short time? Are they actually just a weakly (nuclearly) bonded configuration of these two particles?

 

No, they are not. There is a change at the quark level (down becomes up), mediated by a W boson, and an electron and antineutrino are created.

 

3) why don't they exhibit ideal gas law behavior? I would expect them to behave like a non-combustible form of hydrogen if they were permanently charge-stabilized, but apparently they don't. Is this because they lack the atomic volume that comes with being an atom with electrons orbiting due to electrostatic force?

 

Because they fail to hold to the assumptions of the ideal gas law, namely that they would elastically scatter via the electrostatic interaction. Neutrons undergo significant amount of absorption when they interact. Neutrons might follow some relation that has a similar form to the ideal gas law, but the proportionality constant would be very different. It would exert a much smaller pressure than an identical amount of Hydrogen under otherwise identical conditions.

[Moontanman]

Yeah ydoaPs, I'll help you push him into the pit as for names i think they missed the boat when they failed to name anti-matter protons ... negatons

Edited April 24, 2011 by Moontanman

[lemur]

Neutrons are released in fission reactions as well, and you're going to Hell for the old-trons joke.

I mentioned radioactive decay. Doesn't radioactive decay include fission reactions? So you're saying it was a hell of a pun, then?

 

No, they are not. There is a change at the quark level (down becomes up), mediated by a W boson, and an electron and antineutrino are created.

I don't understand these sub-sub-atomic particles like quarks because they don't appear to have any direct correlation with observable forces. Electrostatics are observable in charge, electricity, and other ways. What do quarks and (anti)neutrinos do?

 

Because they fail to hold to the assumptions of the ideal gas law, namely that they would elastically scatter via the electrostatic interaction. Neutrons undergo significant amount of absorption when they interact. Neutrons might follow some relation that has a similar form to the ideal gas law, but the proportionality constant would be very different. It would exert a much smaller pressure than an identical amount of Hydrogen under otherwise identical conditions.

That raises another question. How can neutrons interact with other particles at all without charge-interaction? What pushes against what?

 

 

[Janus]

as for names i think they missed the boat when they failed to name anti-matter protons ... negatons

 

That was because "negatron" was already an alternative name for the electron, and it would have been too easy to confuse negaton and negatron.

[swansont]

That raises another question. How can neutrons interact with other particles at all without charge-interaction? What pushes against what?

 

They do have a magnetic moment, but the main interaction is via the nuclear force.

[lemur]

They do have a magnetic moment, but the main interaction is via the nuclear force.

So they can add some energy to electrons but mostly they deliver their energy to atoms by collapsing into nuclei? Wouldn't that mean that atoms would have to absorb neutrons? But if they did, wouldn't they become heavy isotopes? I didn't think heavy isotopes could be created as easily as them catching a neutron. Is it that neutrons often "fly by" a nucleus without collapsing into it and thus exert force it while passing by? Or am I being too mechanical again for quantum logic?

[Cap'n Refsmmat]

I didn't think heavy isotopes could be created as easily as them catching a neutron.

http://en.wikipedia.org/wiki/Neutron_capture

[lemur]

http://en.wikipedia....Neutron_capture

Wow, thanks. There seems to be a whole chemistry of nuclear chain reactions involving neutron absorption and (re)emission. After reading the article, I was surprised not to hear graphite mentioned since I have heard of that being used to control the reaction rate before. I had no idea neutrons worked like chemical catalysts in nuclear reactions. I thought they just added energy by colliding with particles at a high speed and thus lots of momentum with their relatively large mass for a sub-atomic particle.

[swansont]

If you're talking about gas-law dynamics, these are thermal neutrons, and are generally moving relatively slow. They have a fraction of an eV of energy. High speed in this context is neutrons with much more energy (MeV).