Talk:Alpha particle

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Energy and production[edit]

Alpha particles are not only produced in decay processes, but also in high energy collisions, when particles with high energy kick out alpha parts from the media. I didnt see this noted (maybe its not needed so). Also I would like to note, that in the introduction, the article says: "and normally a total energy of about 5 MeV", well, in fact this is not true, the term 'total energy' includes the rest mass I think, so it may be more clearer, and precise to say that they have a typical kinetic energy of 5 MeV. Hooverstein (talk) 19:48, 21 August 2009 (UTC).Reply[reply]

Rays vs. particles[edit]

Since Alpha radiation is known to be a couple of protons and neutrons, why should this entry be under Alpha Rays? Surely it should be a redirect to Alpha Particles? -- Dave McKee

A ray is described as a beam of particles, so it is applicable here Albert Einsteins pipe

Result of alpha emission[edit]

I've added something about what happens to an element when it emits and alpha particle, if anyone finds any flaws in my science feel free to edit it Albert Einsteins pipe

Alpha particle emission is a form of nucleon particle decay whereby the energized nucleon is able to get rid of excess kinetic energy of motion by localizing it within the 4 nucleons that make up the potential 4 nucleon alpha particle. this is contrary to the usual conventional concept whereby excess energy is usually more or less evenly divided amongst the nucleons; and implies the existence of certain structural deficiencies in the form of the affected nucleus. This can occur due to either the accumulation of too many excess neutrons by the nucleus (which is more common) or else by the occurrence in the case of 62 Samarium of an insufficient number of excess neutrons to maintain a stable nuclear structure. The result in either case is the creation of a nucleus which is modified by the loss of the 4 nucleons. (plus excess kinetic energy) and is consequently a more stable nucleus.WFPM (talk) 14:48, 2 June 2009 (UTC).WFPM (talk) 20:51, 2 June 2009 (UTC)Reply[reply]
Sounds a little strange to me. The nucleus is pretty much a Fermi liquid. Actually two, as protons and neutrons are distinguishable, so Pauli exclusion is separate. The are, then, moving at up to the Fermi energy of about 38MeV (and so Fermi velocity). The pretty much fill a sphere in k-space up to the Fermi level. It seems to me that they tunnel together for reasons similar to Cooper pairs. I don't know Fermi liquid theory quite well enough to say more, but the common model is alpha particles inside the nucleus moving at up to the Fermi velocity, bouncing off the nuclear boundary (or just outside it, where there is nuclear force only from one side) until they eventually tunnel through. Gah4 (talk) 00:19, 2 October 2020 (UTC)Reply[reply]

Lord Kelvin / JJ Thompson?[edit]

The article states it as Lord Kelvin's Plum Pudding model, but every other source I know of states it as J.J. Thomson's Plum Pudding model, along with the fact the Lord Kelvin isn't accredited with the model on Wikipedia. Maybe they confused their Thomson?


Alpha particles are the exact same thing as a helium-4 nucleus. Is there a reason why we have two articles for the same thing? An alpha ray implies the He-4 nuclei are in motion, but alpha particle does not. Since alpha ray redirects here, I am not sure what to say. If alpha particle = alpha ray, than they are most certainly both equal to He-4. Thoughts? mastodon 21:20, 26 March 2006 (UTC)Reply[reply]

No, it should not be merged. Helium refers to the whole atom, with electrons, while alpha particles are just the nucleus, generally moving at high speed. Helium 4 is an isotope of helium, while an alpha particle is a helium 4 nucleus, samples of pure helium 4 are available, while samples of alpha particle are not. I will remove the merge notice. Polonium 20:45, 30 March 2006 (UTC)Reply[reply]

Helium has 2 electron 2 proton 2 neutron when radioactive rays are passed throgh helium nucli then 2 electron get out from the shell and the alpha rays get to the place of electron and it becomes alphaaparticle

THE EQUATION OF NEUTRON DISCOVERY Berilium atomic no 4 and mass no 9{different isotope}+alpha particle atomic no 2 mass no.4=carbon atomic no. 6 and mass no. 12+ Natomic no.0 mass no. 2{having high penetration power}


If alpha particles have integral spin and are color-neutral, why are they not considered mesons? What facet of the definition of a mesons excludes larger particles like these?

Aren't mesons made of just two quarks? An alpha particle would have twelve quarks.... RobertAustin 13:15, 11 November 2006 (UTC)Reply[reply]

Shape of the Alpha Particle[edit]

Is the alpha particle shaped like a little sphere, a little tetrahedron, or what? Is the answer to this question even known? If it is known, and someone can provide a source, it would make a nice addition to the article. RobertAustin 13:15, 11 November 2006 (UTC)Reply[reply]

With a spin of Zero, it follows that it is the result of the bonding of two deuterons together; and it depends on what you think the spin of the deuteron is. If you think the spin of the deuteron is 1, then you wind up with 1 up deuteron(with spin +1) side bonded to a down deuteron (with spin-1). However there are other possible shapes involved with the possibility that the spin of the deuteron is also zero, and one is that the alpha particle is planar shaped, (made up of 4 side bonded neucleons). see Talk: Nuclear modelWFPM (talk) 14:27, 2 June 2009 (UTC)Reply[reply]
Since deuterons do NOT have a spin of zero, there is no point in discussing the possibility. The two protons and two neutrons in an alpha particle (or a He-4 nucleus) are in 1s orbitals, rather like the two electrons in helium. all 4 particles occupy exactly the same space (since they all have different quantum numbers) and the collection is spherically symmetric. As with the 1s electrons, the nucleons have no angular momentum, so each one spends the maximum time at the center of the particle (has probability/volume highest there), and this decreases with distance rapidly. The nuclei of many atoms have a rather constant density until one reaches the "skin", but due to the fact that all these particles are in orbital with no angular momentum, their wavefunctions look like 1s wavefunctions for hydrogen or helium: high in the center, with a semi-exponential tapering out with distance. SBHarris 21:37, 2 June 2009 (UTC)Reply[reply]
For the life of me, I can't visualize a 4 particle nucleus with spherical symmetry: particularly since I visualize nucleons as cylinders rather than spheres, with an axis of rotation or spin running through the center of the cylinder. So a spin of +1 or -1 is for two end to end connected nucleons with parallel spins, and a spin of zero is for 2 side connected nucleons with antiparallel or opposite spins. And I consider the use of spheres to model nucleons without an arrow indicating their spin direction to be a cop out. And I'm stuck with the idea that the magnetic accumulation protocol discussed in my Talk: Nuclear model is capable of providing indications as to the relative compatibility of interconnection between adjacent nucleons: while I still understand the concept of the spherical range of motion controlled by the 1s orbital. But I do appreciate your comments, and wish I were as confident in my ideas and opinions as you are. So thanks and good luck.WFPM (talk) 05:52, 3 June 2009 (UTC)Reply[reply]
I the classical world, we have spheres, almost spheres, and nowhere close to spheres. But we also have nuclear models made up of spheres stuck together. Pauli exclusion gives electron orbitals (and so atoms) the shape the have, and also give the nucleus its shape. There is no exclusion between particles with different spin, or different particles. Two protons and two neutrons can fit in the space of just one. (To the extent that a proton or neutron is spherical.) In quantum mechanics, there is no such thing as almost. The alpha particle has spherical symmetry, and so is, as well as we can say, a sphere. Gah4 (talk) 04:27, 22 June 2020 (UTC)Reply[reply]
Well, you have no problem appreciating that both H and He atoms are spheres, yes? But H has a net electron spin but He does not, because the electron spins cancel in He. Well, an alpha has its two protons in a pair, and it's two neutrons in a pair, in a 1s exactly like the two electrons in He. No cylinders. SBHarris 06:05, 3 June 2009 (UTC)Reply[reply]
Yes but I'm an Engineer and not an accountant and would like to have a concept as to what an electron spin in a distant no angular momentum orbital really is as a physical entity such as to be capable of canceling each other out. WFPM (talk) 19:06, 3 June 2009 (UTC)Reply[reply]
Admitadly hard to visualize, but again I asK: do you think helium atoms are other than spherical? The very chemical inertness of the He atom comes from the same quantum physics as the stability of the alpha at its core. Filled 1s orbitals. With no angular momentum, the particles sort of swing back and forth on a line, in all directions. So there's no orbital momentum to cancel. As to their intrinsic spin, the waves are obviously somehow in lockstep, so these point in opposite directions. But we don't have a good mechanistic "picture" of what intrinsic spin is, in QM. Personally I think there's something physically missing here also, but whatever it is, would take rotation rates faster than c. SBHarris 23:10, 3 June 2009 (UTC)Reply[reply]
I Think that the volume of space capable of being significantly influenced by the 3 or 4 nucleon core material plus 2 electron mass peripheral material of the Helium atom may be crudely estimated to consist of a spherical volume of 3 dimensional space by those who are unable to determine any directional details of the method of interaction of the materials with that of other matter. And in the case of the charged alpha particle without the electrons we are to believe that the core material is then affected by a repelling electrostatic charge field which is managed by the core materials of the other associated materials. So we have to have some electrostatic field gradient materials available so that the affected helium core materials can sense the gradient and know which way to go. WFPM (talk) 02:54, 4 June 2009 (UTC)Reply[reply]

Alpha Penetration and Detection[edit]

I was recently reading a discussion on a Yahoo group which led me here due to difficulty reconciling what Geiger-Müller tubes can detect vs. what alpha particles can penetrate. According to the GM tube article, "The usual form of tube is an end-window tube. [...] The mica window type will detect alpha radiation but is more fragile." But, according to this article, "Because of their charge and large mass, alpha particles are easily absorbed by materials and can travel only a few centimeters in air. They can be absorbed by tissue paper or the outer layers of human skin (about 40 micrometres, equivalent to a few cells deep)". If alphas are stopped by tissue paper, how can they possibly penetrate mica? One poster in the Yahoo discussion asserts that since alpha emitters are also gamma emitters, that what GM tubes detect from alpha sources is really only the gamma radiation. Another theory is that they can detect alphas only indirectly, if an alpha impact happens to knock loose an electron (beta particle) from the inside surface of the window. If either of these assertions is true, then I believe a correction to the GM tube article is in order.

The mica window is very thin and for this reason very expensive. In the literature, sectional densities of 1.0 to 1.5 mg/cm^2 are given. For simplicity, if you figure mica has density 2.8 g/cm^3, and use a sectional density of 1.4 mg/cm^2 (half that), then the thickness is 1/2000th of a cm = 5 micrometers. If (epidermal) skin is 50 micrometers (st the thinnest-- over the eyelids) and tissue paper 30 microns thick, then it's not completely crazy that they might stop alphas, but a mica window of 3 times the density that is 1/6th or 1/10th as thick, will not. Air has a density of roughly 1.3 kg/m^3 = 1/2000th that of mica. A stopping power of 2 cm in air corresponds then to 1/1000 cm = 10 micrometers in mica. I would suppose that's how they picked 5 microns. SBHarris 18:19, 19 August 2009 (UTC)Reply[reply]

Alpha particles leave very small holes upon collision with mica. This is a fact. In fact, if you don't believe me, get some radium, put it near some mica and then boil the mica in NaOH. The holes will get bigger. It's a plain, simple fact. Bochum 08:53, 6 August 2007 (UTC)Reply[reply]
OK - got a reference for that plain, simple fact? Vsmith 14:23, 6 August 2007 (UTC)Reply[reply]

I'm posting this here because I don't know where such a suggestion should be posted in relation to the GM tube article, because the discussion page there just says something about "This article is within the scope of WikiProject Physics..." with nothing about how/where to go about posting a message such as this one.

Will someone please clarify the last part about alpha particles in computer engineering?

Perhaps the definition should be separated from various subtopics such as hisotircal references and reasoning for the nomenclature. Perhaps using subheadings whereby the concept is defined before it's history is described.

As from studied alpha particles have a charge of +2 but the beta particle has a charge of -1, but respectively the gamma particle has a charge of 0. 08:25, 16 April 2007 (UTC) Dr Mena(MBS) cambridge pressReply[reply]

Copied the above to Talk:Geiger-Müller tube. Vsmith 14:29, 6 August 2007 (UTC)Reply[reply]

Rutherford's gold foil experiment[edit]

I added a link to the separate article covering the experiment, but I think the relatively extensive coverage should be shortened to little more than a mention. Kjetilho (talk) 17:25, 29 June 2008 (UTC)Reply[reply]

Power of ten?[edit]

Raelle.volleyball.21 (talk) 01:28, 9 October 2008 (UTC)I was just wondering what power of ten the alpha particle is...I've been trying to find it EVERYWHERE and I can't!!!Reply[reply]

What do you mean ‘power of ten’? Mass? Size? If mass, look at the infobox, if size, that's a complicated question to ask about a quantummechanical particle. Shinobu (talk) 13:42, 2 December 2008 (UTC)Reply[reply]

Biological effects[edit]

Without a bit of thought or research, if an atom loses an alpha particle, the parent should contain an excess of two electrons. Why should the the nucleus of this donor be attracted to the electrons of DNA?Petedskier (talk) 17:07, 26 September 2010 (UTC)Reply[reply]

Image for types of radiation[edit]

Improved Gif image: — Preceding unsigned comment added by (talk) 10:56, 26 May 2011 (UTC)Reply[reply]

Mass-energy equivalence[edit]

Given the interconvertability of all matter and energy (have you calculated your de Broglie wavelength recently?) the same argument could be made for any type of ray, radiation, or collection of matter. Perhaps what is needed is a convention to use in naming the entries for the types of rays or radiation that have "trivial" names: alpha, beta, gamma. Whether we make the the modified term "ray" or "radiation" is of no import to me, though I think "particle" would be a stretch, since one never speaks of a gamma particle (a high energy photon) and rarely, if ever, of a beta particle (an electron).

I say call them all "radiation" and make any other entry a redirect. -- dja

I think that "alpha radiation" and "alpha particle" are generally used in diferent contexts. Some of my research entails impinging alpha particles upon a device surface to create knock-on and knock-off damage, and the unit for measuring this is "counts" or "number of alpha particles", while it would make less sense to say "one million alpha radiations" -aliencam (talk) 00:21, 4 December 2011 (UTC)Reply[reply]
Matter and energy are not completely interconvertable, as there are many conservation rules that govern the process besides E=mc2. A photon cannot just turn into an alpha-- at best it would need to give an alpha/anti-alpha pair, and the odds of that are long indeed, and the energy needed is HUGE. On the flip side of this, baryons are conserved also, so in the absense of "antibaryons" they can't just disappear into energy. That means your alpha's kinetic energy is usable and convertable (that's how most radiothermal generators work, after all), but that's it. It does make a difference if the radiation is alpha, for after the alpha stops, it becomes helium and that's where most of THAT energy goes to. A child's helium balloon is actually just a bag of retired alpha particles once radiated from actinides in the Earth's crust-- their initial energy (3.727 Gev) is mostly still there, and still unconvertable to anything (unless you have a Wolf-Rayet star handy?). Only their intitial 5 MeV of kinetic energy (0.13%) was ever (in practicality) convertable to other forms of energy. And probably never converted to any mass!

And dja, please don't consider all forms of radiation equivalent. In biology they are not, as these conservation rules govern how they interact with matter, not their total energy. See the article on relative biological effectiveness, for many example of this-- alphas are 20 to 300 times worse than photons, even counting kinetic energy of alphas against total energy of photons. Finally, although in quantum mechanics all particles have wave properties and vice versa, which of these attributes become important depends on yet other rules. One of the reasons photons ultimately act more like fields than particles (expecially at low energies) is that they are massless (a huge impact on their energy/momentum relation, and thus wavelength). Another is that they are bosons (as electrons are not). Being a boson makes a difference even to complex particles, which is why helium-4 easily forms a superfluid, whereas helium-3 does only with great difficulty (and at temperatures far nearer to absolute zero). And so on. Why not actually read this article about alpha particles? You might learn something! SBHarris 02:29, 4 December 2011 (UTC)Reply[reply]

In The Nuclear binding energy article it states that the semi-empirical binding energy formula takes into account that the n-p bond energy is greater than either the n-n or p-p bonds. Wouldn't this indicate that the alpha particle is probably made up of 2 bonded deuteron (1H2) particles?WFPM (talk) 21:54, 12 April 2013 (UTC)Reply[reply]

See also[edit]

Needs a little trimming. All the best: Rich Farmbrough14:04, 25 May 2014 (UTC).


The article currently states:
"If the ion gains electrons from its environment, the alpha particle can be written as a normal (electrically neutral) helium atom 4
This is unclear. How could the species still be an alpha particle if it has gained electrons to become an ordinary (neutral) helium atom?
—DIV ( (talk) 12:48, 25 August 2017 (UTC))Reply[reply]

It is no longer an ion ... fixed. Vsmith (talk) 17:57, 25 August 2017 (UTC)Reply[reply]
Seems that this is all convention. Note that all our helium that comes out of the ground in natural gas originated as alpha particles, and got that name before it was known what they are. We could just as easily call the floating balloons alpha balloons, but that is not common. Once they slow down enough, and grab electrons off whatever is nearby, we call them helium. Gah4 (talk) 18:37, 24 November 2020 (UTC)Reply[reply]

They then caused an electric spark inside the tube, which provided a shower of electrons that were taken up by the ions to form neutral atoms of a gas.[edit]

The article says: They then caused an electric spark inside the tube, which provided a shower of electrons that were taken up by the ions to form neutral atoms of a gas. This sounds a little strange to me. The alpha particles won't be a gas until they get electrons, which they likely will as soon as they hit the wall. As long as they don't go too far into the fall. Do they then stick? You can't get a spark through vacuum, but only through gas. It might be that heat is needed to get them off the wall, though. Gah4 (talk) 00:27, 2 October 2020 (UTC)Reply[reply]

I was about to say this, but it seems that I already did. Gah4 (talk) 18:32, 24 November 2020 (UTC)Reply[reply]