Talk:Radioactive decay/Archive 2

Archive 1

Archive 2

Spontaneous burst

To say that spontaneous radioactive decay occurs in a truly random fashion says nothing. Since science argues that all atoms of a particular element and isotope are truly identical and lack a unique "serial number", all should decay at the very same time or never, for they have no inherent difference that could differentiate among them!

This is in contrast with what we observe. Therefore, there must be a mechanism that individually identifies atoms and "draws lots" from the configuration space of the information universe, to find out which single atom should "spontaneously" decay at any given time and somehow individually "pings" the unlucky one to induce the decay.

Yet, this WP article says nothing about science's effort to find out, how and where the "NIC addresses" of individul atoms are stored in nature, as well as the search to identify the "CAT5 cable" that connects individual atoms to the configuration space, so that they can be pinged to decay if the "Ultimate Dice-thrower" decides its game over for that atom.

Indeed, one can write pretty math equations for truly random spontaneous decay, but that does not explain the physical mechanism by which such is induced to effect. Contrary to the currently fashionable notion that Universe = Mathemathical Information, there are many trans-computable processes, from 3-body problem to turbulent flows, that show matter and energy are more existant than maths!

This mandates a big change in the tone of this article. In fact, treatise on "spontaneous radioactive decay" should become a separate article, because of its deep philosophical, theophysical and experimental implications! 82.131.210.163 (talk) 12:11, 20 April 2012 (UTC)

I was responsible for the mathematics section, and have trimmed it to the more essential content. Hope it is ok. Maschen (talk) 10:53, 15 September 2012 (UTC)

"Random" means unpredictable. We say that radioactive decay is "random" because it is practically unpredictable. That is, We have no scientific theory that predicts when a given nucleus will decay. That does not mean that there is no reason why a nucleus decays: It only means that we don't know the reason.

When you say, "there must be a mechanism that individually identifies atoms and..." That is a theory---your theory. Until your theory is backed up by published, and widely accepted scientific research, it does not belong in a Wikipedia article. 129.42.208.183 (talk) 23:21, 30 January 2014 (UTC)

I frown upon the fact that a small company website which only mentions this issue in passing, without justification or considerations of any kind, is passed off as an authoritative source on the metaphysical interpretation of quantum theory. (See the current 1st citation: http://www.iem-inc.com/information/radioactivity-basics/decay-half-life). 141.39.226.227 (talk) 19:47, 25 April 2015 (UTC)

The mechanism for alpha decay is pretty well understood. Quantum mechanically, you can consider the nucleus as made up of alpha particles, plus an additional odd neutron and/or proton. The alpha particles move at the fermi velocity, trying to escape, but are held back by the nuclear binding (strong) force when they hit the surface. Each time, there is some probability of Quantum tunnelling through the barrier. Statistically, it is many many trials with very low odds, until it escapes. Statistical randomness is a fundamental part of quantum mechanics. Gah4 (talk) 00:42, 13 October 2016 (UTC)

The statistics name for this is memorylessness. That atom doesn't remember how long, it just keeps trying to decay. Gah4 (talk) 08:15, 13 October 2016 (UTC)

A radioactive source emits its decay products isotropically

A radioactive source emits its decay products isotropically As noted with the recent change, this isn't, in general, true. Assuming that the nuclear orientation in space is isotropic, (that is, statistically independent) then it is naturally true. I suppose it should also be for spin zero nuclides. But nuclides with spin are not isotropic, and when spin aligned, the decay products likely aren't, either. Gah4 (talk) 09:08, 13 October 2016 (UTC)

Niépce's discovery

It is unclear from the articles on Abel Niépce de Saint-Victor and Henri Becquerel what exactly is Becquerel's discovery with respect to Niépce's work, or indeed if Becquerel deserves credit for the discovery of radioactivity. The current state of the Intro to the History section seems especially inappropriate because Becquerel seems to have had prior contact with Niépce's work.

Somebody should volunteer a bit of research and improve these 3 articles ;) 213.149.51.245 (talk) 07:46, 17 March 2017 (UTC)

Looking at Abel Niépce de Saint-Victor, it mentions uranium salts, but not uranium metal. Looks to me that Henri Becquerel figured out that it was an elemental property. With the advancements in chemistry and physics over those years, it would have been pretty surprising that much earlier. Also, Becquerel used dry plates exposed over days. In the days of wet plate photography, that would have been much more difficult to do. It is easy to look back now, and figure out that with a little more work, Niépce would have discovered radioactivity, but harder to do it from the viewpoint of the day. Gah4 (talk) 19:02, 17 March 2017 (UTC)

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⁸
₄Be

The article indicates that only elements of atomic number 52 and higher alpha decay, but there is one more case: ⁸
₄Be
. It is a little unusual, but it seems to be the usual description of its decay mode. Gah4 (talk) 08:11, 1 August 2017 (UTC)

True. I have now added Be-8 to the sentence on alpha decay. Dirac66 (talk) 00:36, 4 August 2017 (UTC)

And I have also mentioned Be-8 in the article on alpha decay. In both articles, I have noted that the decay is to two alpha particles, which seems the best description of the "unusual" nature. Dirac66 (talk) 01:22, 4 August 2017 (UTC)

Lower limit to half-life

The text says, "no known natural limits to how brief or long a decay half-life for radioactive decay of a radionuclide may be." Since there is a lower limit to time itself (planck time) it would seem that no half-life could be less than two planck times. So there is a known limit to how brief a decay half-life of a radionuclide could be. I flagged the claim with a citation tag to see if there are any sources that might contradict my OR on this (or confirm it). Sparkie82 (t•c) 23:53, 29 March 2019 (UTC)

Seems to me that it has to be long enough to be two decays instead of one. There is also the QM time-energy uncertainty. I don't think it makes sense to give a time less than the nuclear diameter divided by c (for special relativity reasons). Gah4 (talk) 02:40, 30 March 2019 (UTC)

The two suggestions above have very different values. The Planck time is of the order of 10^-44 sec, while the nuclear charge radius is of the order of 10^-15 m, so that the nuclear diameter divided by c is about 10^-25 sec. As stated in the section Theoretical basis of decay phenomena, the shortest half-life known is about 10^-23 sec for ⁷H, so it would seem that the nuclear diameter gives a more useful estimate than the Planck time. Now we need to find a reliable source to justify using the nuclear diameter (or radius). Dirac66 (talk) 15:06, 31 March 2019 (UTC)

I agree. This raises another issue about the definition of exactly when a nuclide is considered "decayed" (also, exactly when it is considered created) for purposes of measuring half-life. That is, what portion of a wavelength must an emission travel before it is considered "emitted" from the nucleus. A discussion of that might be a useful addition to the article. Sparkie82 (t•c) 07:37, 1 April 2019 (UTC)

For some particles, nuclear emulsion is used, where the decays occur inside a thick photographic emulsion. You then measure the distance under a microscope, and from the velocity calculate a time. The limit, then, is microscope resolution dependent, but significantly more than nuclear diameter over c. Gah4 (talk) 09:09, 1 April 2019 (UTC)

List of decay modes 2016

This is a full list of decay modes, listed in {{NUBASE2016}} p.20:

Decay modes

α =α emission

p, 2p =proton emission; 2-proton emission

n, 2n =neutron emission; 2-neutron emission

ε =electron capture

e+ =positron emission

β+ =β+ decay (β+=ε+e+)

β− =β− decay

2β− =double β− decay

2β+ =double β+ decay

β−n =β−delayed neutron emission

β−2n =β−delayed 2-neutron emission

β+p =β+ delayed proton emission

β+2p =β+ delayed 2-proton emission

β−α =β− delayed α emission

β+α =β+ delayed α emission

β−d =β− delayed deuteron emission

IT =internal transition

SF =spontaneous fission

β+SF =β+delayed fission

β−SF =β−delayed fission

...list is continued in a remark, at the end of the A-group

For long-lived nuclides:

IS Isotopic abundance (from [2011Be53]) [i.e. from AME2011, replaced by {{AME2016 II}}, DePiep)

It occurs to me that the table in Radioactive_decay#Types of decay could be checked against this list. -DePiep (talk) 17:51, 4 July 2019 (UTC)

References

• How is their β⁺ different from the plain positron emission? Incnis Mrsi (talk) 17:56, 4 July 2019 (UTC)

I don't know about the physics, but in the NUBASE list (I copied) it says:

e+ =positron emission

β+ =β+ decay (β+=ε+e+)

so the difference you look for is the "ε+" right? OTOH, indeed our article positron emission says different (so enwiki is wrong?). -DePiep (talk) 19:54, 4 July 2019 (UTC)

This is a new Nubase notation as explained at the bottom of page 8 (marked 030001-8). β+ = ε + e+ means that electron capture (ε) and positron emission (e+) occur in competition, so that some nuclei in the sample decay by ε while others decay by e+. At lower energies (less than 2 m_ec²), e+ is impossible so only ε occurs.

There is a subsequent remark saying that β+ = ε + e+ was written in a previous document which they name ENSDF (= Ref.5 dated 1990 I think) as ε + β+, so β+ has changed meaning between the two documents! This is quite confusing and Wikipedia should mention both notations to help the reader. Dirac66 (talk) 20:45, 4 July 2019 (UTC)

Ouch.

I will add a column to the table for these symbols & abbreviations (α, SF, etc). Issues to be handeled in article (describe, footnote). -DePiep (talk) 20:07, 9 July 2019 (UTC)

• A template now, with symbols column. Improvements welcome in Template:Decay modes(edit talk links history). -DePiep (talk) 21:08, 9 July 2019 (UTC)

Theoretical basis of decay phenomena

There is a question in the section Theoretical basis of decay phenomena about WP:OR. I suspect that some is, but I don't know which. There is, however, one case that I believe is well described. You can consider most of the nucleons on the nucleus as moving alpha particles. (That is, quantum states where two protons and two neutrons are in the same state.) These alpha particles then move at the fermi velocity and run into the potential barrier at the nuclear boundary. There is a possibility of Quantum tunnelling each time it hits the potential barrier at the nuclear boundary. Since tunnelling is exponential, it is easy to explain the large range of decay times. Gah4 (talk) 01:56, 22 August 2019 (UTC)

“These alpha particles [that] move at the fermi velocity”? A fine piece of junk physics. For the record I have nothing against tunnelling through a potential barrier – this metaphor was used by respectable 20th-century physicists as a quick-and-dirty explanation of the exponential law, as well as huge diversity in lifetimes. Incnis Mrsi (talk) 08:04, 23 August 2019 (UTC)

particles

There seems to be some question as to gamma photons being subatomic particles. Photons are particles, so that should be fine. If the wavelength is smaller than a typical atom size, then they are subatomic. Some might be low enough energy to have a wavelength bigger than a typical atom, but most don't. Gah4 (talk) 23:58, 18 December 2019 (UTC)

The weak force is the mechanism that is responsible for radioactive decay.

Does this apply to all forms of decay? Or is alpha decay caused by the electromagnetic force?--Klausok (talk) 06:11, 5 March 2020 (UTC)

Beta decay is weak force, along with its non-conservation of parity. Alpha is strong and electromagnetic, not weak force. Strong force binds quarks to make nucleons. Residual strong force binds nucleons in the nucleus. Pauli exclusion (exchange force) keeps nucleons from getting too close (with shells similar to electron orbitals), and sets the Fermi velocity. Pairs of neutrons and protons can be considered moving around inside the nucleus at the Fermi velocity and tunnel through the potential barrier, eventually escaping. Only strong and electromagnetic force apply. Gah4 (talk) 13:02, 5 March 2020 (UTC)

Then the lead needs changing. However, since this sentence has a reference, and I have no reference, I am not going to remove it. --Klausok (talk) 20:52, 5 March 2020 (UTC)