Understanding Alpha Decay: An Explanation and Potential Risks

In summary, alpha decay is a process in which a nucleus emits a clump of 2 neutrons and 2 protons, known as an alpha particle. This particle is highly energetic and can be stopped by the skin or a sheet of tissue paper, where it becomes a neutral helium atom. Alpha particles are deadly if ingested because they can cause damage to vital molecules in cells. There is currently no satisfactory theory for alpha decay due to the lack of a complete theory of nuclear forces. However, the sharp dependence of decay time on the energy of the alpha particle can be explained by considering the particle's energy state within the nucleus and the Coulomb potential it must overcome to escape. This explanation has been observed to match with experimental data
  • #1
McLaren
I've searched the web madly, but I can't find a thorough explanation of alpha decay.

When a nucleus is unstable, it emits a clump of 2 neutrons and 2 protons, and this is called an alpha particle. Is this right?

As for the 2nd question. Why are alpha particles deadly if ingested? After all, the alpha particle is in the form of a helium nucleus, and if helium is inhaled it will just make your voice high pitched. Does anybody have an answer?

Any help would be greatly appreciated.:smile:
 
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  • #2
Some answers

The Helium nucleus has a high binding energy and that is why it is thrown out during decay as opposed to other nuclei.

It's deadly if you ingest an alpha emitter because the alpha particle can tear up vital molecules in a cell, disrupting cell funtion and even causing cancers.
 
  • #3
Originally posted by McLaren
I've searched the web madly, but I can't find a thorough explanation of alpha decay.

When a nucleus is unstable, it emits a clump of 2 neutrons and 2 protons, and this is called an alpha particle. Is this right?

As for the 2nd question. Why are alpha particles deadly if ingested? After all, the alpha particle is in the form of a helium nucleus, and if helium is inhaled it will just make your voice high pitched. Does anybody have an answer?

Any help would be greatly appreciated.:smile:

Hi McLaren,
You are right about the composition of an alpha particle; It is easily stopped by the skin or a sheet of tissue paper where it becomes a neutral Helium atom having collected two electrons. Often with alpha emission [also with beta (an electron) emission] there is one or more gamma rays which are really penetrating. With U-238 there is 4.2 MeV alpha coincident with a 45 - 50 kilovolt gamma ray. With U-235 the alpha is about 4.4 MeV along with a 53 KeV gamma ray. Cheers, Jim
 
  • #4
There is indeed no satisfactory alpha-decay theory because there is no satisfactory theory of nuclear forces yet (QCD is still in development phase).

So, explanation of sharp dependence of decay time versus energy of alpha particle goes as follows. Alpa particle is kinda "already there", in the nucleus, on some state (energy level) which is well above "ground" (~few MeV) if by "ground" here we mean its energy far away from nucleus. It is kinda moving back and forth inside nucleus in compliance with HUP, and is bouncing from tall walls of nuclear potential in desperation to leak out. The barrier it has to overcome sharply depends on energy of particle, because the outside wall of this barrier is simply a Coulomb potential of repulsion of alpha particle from the rest of the nucleus (U~1/r hyperbola) - it is thick and fat at low energies and quite thin at high.

So, if energy state of alpha particle is 7-8 MeV above "ground", it leaks via barrier quite fast (in seconds and less), if 5-6 MeV - years, and if less than 3-4 MeV - billions and trillions of years.

Of course, there is no alpha particle as an isolated entity in the nucleus before it desintegrates. (And strictly speaking so can be said about protons and neutrons themselves - in nucleus they constantly swap color exchanging by gluons). So it is not clear why this explanation kinda works (predicting relation between energy of alpha particle and decay time, which matches observations).

And I don't know if there is better (or alternative) explanation for alpha decay to date. May be somebody else here knows?
 
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1. What is alpha decay?

Alpha decay is a type of radioactive decay where an atom's nucleus emits an alpha particle, which is made up of two protons and two neutrons. This results in the parent atom's atomic number decreasing by two and its atomic mass decreasing by four.

2. How does alpha decay occur?

Alpha decay occurs when an atom's nucleus is unstable and has excess energy. The nucleus releases this excess energy by emitting an alpha particle, which reduces the overall energy of the nucleus and makes it more stable.

3. What are the potential risks associated with alpha decay?

The main risk associated with alpha decay is exposure to harmful radiation. Alpha particles are large and heavy, which makes them less able to penetrate materials or skin. However, if alpha-emitting radioactive materials are ingested or inhaled, they can cause damage to internal tissues.

4. How is alpha decay used in scientific research and technology?

Alpha decay is used in various scientific research and technological applications. It is commonly used in nuclear power plants to produce energy, as well as in medical treatments such as radiation therapy for cancer. It is also used in radiometric dating to determine the age of rocks and fossils.

5. Can alpha decay be artificially induced?

Yes, alpha decay can be artificially induced through processes such as nuclear fission or fusion. However, this requires a significant amount of energy and is typically only done in laboratory settings for research purposes.

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