Forces are actually involved in radioactivity

[EIRE2003]

What forces are actually involved in radioactivity other than the weak nuclear force?
And would anyone know any nice animations that one could view on the net of radioactive decay processes?
Thanks

 

[mathman]

Alpha decay involves strong nuclear force as well as electromagnetic, not weak force.

 

[Vixus]

As far as I can see, when the strong nuclear force applied by the neutrons in a nucleus can no longer overcome the force of the protons repelling each other, alpha decay occurs.
So I guess it involves EM and strong nuclear force in this case.

Beta particles are emitted when there are too many neutrons and a beta particle is emitted when a neutron decays into a proton and an electron (the particle).

Correct me if I'm wrong >_<

 

[EIRE2003]

Is the weak nuclear force only involve the decay of quarks and leptons?

 

[ZapperZ]

As far as I can see, when the strong nuclear force applied by the neutrons in a nucleus can no longer overcome the force of the protons repelling each other, alpha decay occurs.

No.. the strong force is many, many times stronger than the coulomb repulsion. The stability or instability of an atom or nucleus has never been influence by the EM forces. If that were the case, there's no reason why adding an electrically neutral neutron to a nucleus would make it unstable.

Beta particles are emitted when there are too many neutrons and a beta particle is emitted when a neutron decays into a proton and an electron (the particle).

Yikes. You need to look up "weak interactions".

Zz.

 

[Vixus]

Haha... well, I haven't studied this stuff yet. :P
Ah, I see. So can you clarify it a little for me?

 

[EIRE2003]

And a positron is emitted when a proton decays to a neutron?

 

[Vixus]

With a neutrino...

 

[ZapperZ]

And a positron is emitted when a proton decays to a neutron?

Er... where do you get this stuff?

A proton decay, if it actually happens, will not be via a channel that has a neutron has a daughter product. This will severely violates conservation of energy/mass. If the Standard Model prediction is correct (where's Benlillie when I need him?), I believe the dominant channel for a proton decay is to a positron and a pi0 meson.

Zz.

 

[Astronuc]

Positron emission occurs when a proton in a nuclear transforms to a neutron, with an emission of a neutrino. See the frame below this one - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3.

 

[chroot]

Beta decay is the reaction: neutron -> proton + e- + electron anti-neutrino.

- Warren

 

[ZapperZ]

Positron emission occurs when a proton in a nuclear transforms to a neutron, with an emission of a neutrino. See the frame below this one - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3.

Where exactly on that page is this described? That page only describe beta decay. This is not proton decay.

Zz.

 

[Astronuc]

If one uses this link - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3 - one had to look at the frame (plate) below entitled "Positron and neutrino" which should be http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c4, but I had problems with the link, but now it seems to work.

But I like Warren's equation $p\,\rightarrow\,n\,+\,e^+\,+\,\nu_e$

Here's how a chemistry site writes it - http://dbhs.wvusd.k12.ca.us/webdocs/Radioactivity/Writing-Positron-EC.html

 

[Rade]

Positron emission occurs when a proton in a nuclear transforms to a neutron, with an emission of a neutrino. See the frame below this one - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3.

Yes, there are two types of "beta decay", b- decay (also called nagatron decay) and b+ decay (also called positron decay). Positron decay involves [P] ---> [N] + [b+] + [neutrino]. This decay of course does not happen to a free proton, only to protons within isotopes. Thus, one isotope decays into another via positron decay--it is not a free proton involved in this type of decay. It is energetically only possible when the mass of the parent isotope is greater than the mass of the daughter isotope by two electron masses. As far as is known, the "free" proton is very, very stable (never decays !--or at least it has never been experimentally observed). Also, positron decay is very well known and used in medical research such as PET scan--see this link:http://www.radiologyinfo.org/content/petomography.htm
It is a hypothesis of some nucleon cluster models that positron decay would be predicted in those isotopes that have a [PP] halo structure in outer nuclear shell, which is very, very unstable. One can see how positron decay of one of the halo [P] nucleons would result in a very stable [NP] cluster structure (called the deuteron).

 

[ZapperZ]

If one uses this link - http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c3 - one had to look at the frame (plate) below entitled "Positron and neutrino" which should be http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/beta.html#c4, but I had problems with the link, but now it seems to work.
But I like Warren's equation $p\,\rightarrow\,n\,+\,e^+\,+\,\nu_e$
Here's how a chemistry site writes it - http://dbhs.wvusd.k12.ca.us/webdocs/Radioactivity/Writing-Positron-EC.html

Maybe I'm missing something, but I still don't see a proton decay channel being shown in that page. And chroot's "equation" is for a typical beta decay. Why are you able to use that as your proton decay? If you look closely, there's a major energy conservation violation on the left side when compared to the right side of the "equation". The starting point (proton) has less mass than the daughter particles. I can understand if the parent particle has a greater mass than the sum of the daughter particles, but for the other way around, something else has to come in and participate. This is not the proton decay.

Zz.

 

[Norman]

The proton decay channel only happens in nuclei- not in free space. Energy is conserved due to the proton to neutron ratio being too high in the nuclei and it becomes energetically favorable for the nuclei as a whole. This site says it never happens naturally- that is outside of a man made reactor.

http://www.antonine-education.co.uk/Physics_A2/Module_5/Topic_4/TOPIC_4.HTM

 

[Astronuc]

Maybe I'm missing something, but I still don't see a proton decay channel being shown in that page. And chroot's "equation" is for a typical beta decay. Why are you able to use that as your proton decay? If you look closely, there's a major energy conservation violation on the left side when compared to the right side of the "equation". The starting point (proton) has less mass than the daughter particles. I can understand if the parent particle has a greater mass than the sum of the daughter particles, but for the other way around, something else has to come in and participate. This is not the proton decay.
Zz.

That is true about proton decay in free space. Certainly to make this rigorously correct, I would have to attach some number of additional nucleons to both sides of the equation. I did not mean to imply that a free proton spontaneously decay by positron emission.

$p\,(in\,_{12}Mg^{23})\,\rightarrow\,n\,(in\,_{11}Na^{23})\,+\,e^+\,+\,\nu_e$

Mg 23 - 22.994123669 amu
Na 23 - 22.98976928087 amu and the Na is lighter despite the fact that Na has more neutrons - the difference obviously being the binding energy.

 

[Rade]

The proton decay channel only happens in nuclei- not in free space. Energy is conserved due to the proton to neutron ratio being too high in the nuclei and it becomes energetically favorable for the nuclei as a whole. This site says it never happens naturally- that is outside of a man made reactor.
http://www.antonine-education.co.uk/Physics_A2/Module_5/Topic_4/TOPIC_4.HTM

This website is incorrect. It is known that K-40 (a natural isotope) has a small % decay mode for positron decay to Ar-40--see below from wikipedia:http://en.wikipedia.org/wiki/Potassium
"There are seventeen known isotopes of potassium. Three isotopes occur naturally: K-39 (93.3%), K-40 (0.01%) and K-41 (6.7%). Naturally occurring K-40 decays to stable Ar-40 (11.2%) by electron capture and by positron emission, and decays to stable Ca-40 (88.8%) by beta decay; K-40 has a half-life of 1.250 × 109 years."

 

[EIRE2003]

Ok so getting to the point, the only forces involved with radioactivity of an atom are the weak nuclear and the strong nuclear forces?
How exactly does the strong nuclear force come into it?

 

[Astronuc]

This might help.

Basic overview of radioactivity
http://hyperphysics.phy-astr.gsu.edu/hbase/nuclear/radact.html#c1

Fundamental forces
http://hyperphysics.phy-astr.gsu.edu/hbase/forces/funfor.html

http://hyperphysics.phy-astr.gsu.edu/hbase/forces/fforcon.html#c1

 

[Leopold Infeld]

I have heard that the average proton life time is 10^34 years or something. And another thing is that neutrinos hit the unstable nucleus of an atom and interact thru the weak force causing beta decay.

 

[EIRE2003]

And another thing is that neutrinos hit the unstable nucleus of an atom and interact thru the weak force causing beta decay.

Yes! You have just read my mind because in actual fact I was just about to ask the question, when the neutron decays to a proton via the W minus particle, does the emitted electron (Beta Particle) fly off into space or is it captured into an energy shell? During this process are there any emissions of electromagnetic energy? Or does that only occur with highly radioactive elements such as uranium?

 

[Leopold Infeld]

Yes, I have wondered about that too. Now that after beta decay has occurred, there has to be one more proton which means that there has to be one more electron too so that it can be a neutral atom. Where does the atom get the electron from? From the beta decay or whether from its surrounding free electrons?

I think that it will choose whatever is convenient since ionised molecules will eventually get their deperived electrons.

Please correct me if I am wrong. I am still a high school sophomore.

 

[Astronuc]

http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html

For the neutrino interaction with an atom, see - http://hyperphysics.phy-astr.gsu.edu/hbase/particles/neutrino.html#c4 - which describes the method used by Raymond Davis to discover neutrinos from the sun.

Also see Cowan and Reines experiment - http://hyperphysics.phy-astr.gsu.edu/hbase/particles/cowan.html

Neutrinos usually have energy in the high keV or MeV range, so the electron will have more kinetic energy than the binding energy to the atom. It will travel some distance, slowing down by collisions with other electrons. There will be a cascade reaction as ions absorb electrons until the system again establishes charge neutrality.