Talk:Radioactive decay

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Introduction has grown too long[edit]

The introductory paragraph is entirely too detailed and much of the material therein needs to be moved to later paragraphs and trimmed out of the intro. — Preceding unsigned comment added by Zedshort (talkcontribs) 20:38, 1 April 2012 (UTC)

Says you, after adding positron capture back into the lede, when it is a hypothetic process never yet seen, and only possible in complex-nuclei antimatter (maybe Captain Kirk and Spock see it in their engines). That's pretty hypocritical. There are NOT "five" processes of radioactive decay, but as many or more as appear in the table, and these don't count hypothetical ones. Just because you count five in a set of college class notes (your reference) [1] doesn't mean five is the number. Moreover, Internal conversion is a far more common process in nature than spontaneous fission, so if you're going to mention these in the lede in order of importance, try following your own rules and suggestions. SBHarris 20:48, 1 April 2012 (UTC)
My attempts are only constructive and not to insult. The illustration in the body of the text suggests and most any reference would mention five methods. While positron capture has not yet been witnessed experimentally that does not make it of no interest. As far as anti-matter reactions go, I am sure you know there is positron emission from nuclei. Which process is most common is interesting and I suppose the order in which they are listed might reflect that. Once again the lede is entirely too long. Please try to stay on subject and to not try to smear me by using pejorative references to Star Trek it sounds adolescent. No one of us owns this article.
  • Please sign your edits. Use four tildes like this: ~~~~. You've been here since October and it's high time you learned the basics of editing.
  • I'm sure your edits were good faith and meant as constructive. However, they were not, as you are adding false information and promoting things of little interest (positron capature) to the lede.
  • This lede is indeed too long, but the way to cut a lede is to avoid mentioning trivia. A process that has never been detected (positron capture) is trivia. You can mention it farther down in the article.
  • Positron capture is not positron emission. The latter happens commonly, and might be mentioned in the lede as a type of beta decay (technically it is beta-plus decay).
  • There are no illustrations "in the body of the text" that show five types of radioactive decay and it would not matter even if there were. There are not 5 types and anybody illustating five types would just show themselves as an ignorant illustator. No, "most any reference" at the college or grad or research level would mention far more than 5 types types of decay, including internal conversion and emission of protons and neutrons.
  • References to Star Trek are to point out that science fiction processes like positron capture should be discussed as hypotheticals (since SF does come true, as in the moon landing). We have seen antimatter, but never the complex higher atomic number type we would need to see, in order to see positron capture. One would need at least anti-beryllium-7 (complete with at least one positron in an atomic orbital) to see it. However, such hypotheticals are not lede material, in a lede that is already too long.
  • Of course nobody WP:OWNs this article, and I welcome comments from people who actually know enough about radioactive decay to know that there are not "five types" of it, as you keep insisting. That makes me think you haven't even read the article you're editing. Could you please do that? SBHarris 23:37, 1 April 2012 (UTC)

>Actually, I have read the entire article and like most articles on wikipedia it is cluttered, poorly phrased and needs reorganizing, hence my attempts. I am sorry if I gave offense by adding the hypothetical process of positron capture but I find the potential of that process interesting and like to include it just for the sake of completeness. If there are more than five processes of radioactive decay I think they should all be added. Perhaps a table of those dozen or more methods would be the best format with all the products included. But from most of the sources I have read typically only three or five are listed. I wonder, have we had a dispute somewhere in the past as you seem to have taken offense at my being here and making these changes? I think I remember you adding to the article on the Energy-Catalyzer. Sincerely — Preceding unsigned comment added by Zedshort (talkcontribs) 00:40, 2 April 2012 (UTC)

You say you've read the article? So how is it that you somehow missed seeing the very table that you ask for? I guess you didn't read it very carefully, eh? And you're still not signing your messages; I suppose you prefer not to learn? And no, I've never edited Energy Catalyzer. SBHarris 00:52, 2 April 2012 (UTC)

The general solution to the recursive problem are given by Bateman's equations[edit]

Hi,

the general solution to the recursive problem by Bateman's equations does not seem to be correct. The correct equation is shown at http://www.physicsforums.com/showthread.php?t=452474

may be someone can change this, with best wishes Wolfgang — Preceding unsigned comment added by 212.95.7.181 (talk) 12:58, 12 April 2012 (UTC)

I see that Bateman's equations for the general case have now been placed in this article. Should we also note that Bateman's equation for the two-decay case is in the article on Transient equilibrium? I am not certain whether it is the same Bateman's equation. Dirac66 (talk) 16:28, 12 April 2012 (UTC)

Hello all. The formula for Bateman's equations given in the physics forum link above and now on the wikipedia page does not agree with that given in Kenneth S Krane's Introductory Nuclear Physics (Unit II Nuclear Decay and Radioactivity, Chapter 6 Radioactive Decay, Page 173 in my copy). Krane doesn't have the decay constant after the sum term in the Nd formula. If someone could confirm and change I'd be much obliged. [This comment by 86.177.136.35, 24 June 2012]

Strange. If we take the equation now in the article and omit the λi after the sum as you suggest, then the units come out wrong. There will be a λD with units of reciprocal time in the denominator which does not cancel, so ND will have units of time. I don't have Krane's book, but it would seem that either he has erred or you have read him wrong. Perhaps someone can check Ref.8, the article by Cetnar. Dirac66 (talk) 23:04, 24 June 2012 (UTC)
Ah, that may be because of a disagreement between this article and Krane for the Ci equation. In this article there is only one product symbol. Krane has separate product symbols for the numerator and denominator and only the denominator is neglected for i=j. I think this would lead to dimensions T^D on the numerator and T^D-1 on the denominator? Edit: A possible test presents itself: the Bateman equation for the case where D=2 is widely quoted. Derive the Bateman equation for D=2 using the method given here and the method in Krane and compare against another reference source? [This comment also by 86.177.136.35, 24 June 2012]
Aha. The extra factor in Krane's numerator is the λi which the formula now in the article (which cites Cetnar's paper) places before the one product symbol. So the two formulas are equivalent, and the only question is which is the clearer presentation for this article. I vote for the one now in the article since it shows the λi explicitly. (And to sign your posts, click on the four ~ below, 4 lines under the Save page button on the right.) Dirac66 (talk) 01:40, 25 June 2012 (UTC)
Of course! My apologies for being so dense. Thank you for clearing that up. 86.148.86.94 (talk) 22:25, 25 June 2012 (UTC)

Spontaneous burst[edit]

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)

Changing decay rates[edit]

Otto Reifenschweiler also observed changes in decay rates in Tritium Reduced radioactivity of tritium in small titanium particles (published in Physics Letters A.)

Claus Rolfs has performed experiments in which he accelerated radioactive decay Half-life heresy: Accelerating radioactive decay

Should these two also be mentioned in the section ? --POVbrigand (talk) 14:13, 7 May 2012 (UTC)

Rate of radioactive decay influenced by "the Sun".[edit]

The theory as I read it was that the rate at which neutrinos pass through a body can influence the rate of radioactive decay of that body. Since the overwhelming proportion of neutrinos passing through the earth (or indeed our easily accessive solar system) is from the sun (an "almost" point source of neutrinos at planetary distances), then obviously any change in the neutrino-producing component of solar activity will change the neutrino flux and hence the radioactive decay rate, as will the distance from the Sun. But to repeat, I have no reference for it, so I'm only including it here as an anecdote.

The other significant part of this is that IF it is true, then with neutrinos passing through solid matter so easily, their effect on radioactive decay will be felt equally on the surface of the earth as it would be inside the earth, and at any depth. 124.184.13.246 (talk) 08:56, 31 August 2012 (UTC)

If you search manganese + radioactive + neutrino on your favorite search engine, you will find many results. There is no theory here. The physicists (Fischbach and Jenkins) who published that took a guess that it might be because of neutrinos. They also took into consideration 30 year old data and considered equipment related anomalies, but how can you do that if you don't have the equipment. The isotope they talk about is Mn 56. They also talk about a solar flare in Dec 13, 2006. Does a solar flare emit neutrinos? I though you get neutrinos when you have beta decay. Anyway, what is so special about a solar flare? Vmelkon (talk) 07:00, 13 October 2013 (UTC)

Prediction of very long decay rates.[edit]

For example, the article on Cadmium states that: "The two natural radioactive isotopes are 113Cd (beta decay, half-life is 7.7 × 10^15 years) and 116Cd (two-neutrino double beta decay, half-life is 2.9 × 10^19 years)." How is such an extraordinarily long decay rate calculated/predicted? 124.184.13.246 (talk) 09:01, 31 August 2012 (UTC)

Try asking the reference desk. Wikipedia:Reference desk/Science --Klausok (talk) 11:20, 31 August 2012 (UTC)

The values are calculated for exponential decay using the measured decay rate -dN/dt = λN, where λ = 1/τ = decay constant. Then λ = -(1/N)dN/dt, and the half-life t1/2 = τ ln 2 = (ln 2)/λ = (N ln 2)/(dN/dt). Dirac66 (talk) 20:08, 15 September 2012 (UTC)

Please spell check[edit]

Look for 'isomeric' instead of 'isometric' and if doing this myself is not illegal please reply telling me that i should have done then and thereKhpatil (talk) 14:54, 7 December 2012 (UTC)

Isomeric occurs 3 times in the article, and it is the correct spelling in the context of radioactivity. An isomeric transition in nuclear physics involves the decay of a nuclear isomer with emission of a gamma-ray. Isometric on the other hand has no meaning in radioactivity or nuclear physics which I know of. Dirac66 (talk) 19:15, 7 December 2012 (UTC)

Are you CRAZY??[edit]

Quote: "Primordial nuclides found in the earth are residues from ancient supernova explosions which occurred before the formation of the solar system."

EVIDENCE for this? ANY? EVIDENCE? AT ALL? — Preceding unsigned comment added by 78.156.126.230 (talk) 15:36, 20 December 2012 (UTC)

The Nucleosynthesis article seems reasonably cited. DMacks (talk) 16:08, 20 December 2012 (UTC)
Wikipedia articles should not cite each other (see WP:CIRCULAR), so I will remove the cite of nucleosynthesis. Also, the statement is inaccurate. The lighter nuclides come mostly from big bang synthesis and ordinary steller synthesis. RockMagnetist (talk) 17:02, 20 December 2012 (UTC)
Keep panties on. This is an article on radioactive decay and the statement above clearly was meant to refer to radioactive primordial nuclides, of which there are 34 (Te-130 was erroneously reported radioactive but this was retracted). The lightest of these is K-40 so (with that possible exception, and we don't know the ratio) all are comfortably supernova products not AGB or Big Bang material. That was the point of the initial statement above, which I've now qualified so there can be no misunderstanding. I can't tell if our incredulous IP objector is a red giant star fan or a creationist or what. Finally, referring to another article which is well-referenced from without is hardly a violation of WP:circular. Somebody needs to read WP:SS. The conclusion here isn't central to this article subject and we don't need the burden of refs for it. If you must have one or two, fine, but it's not controversial and is a waste of space. SBHarris 20:41, 20 December 2012 (UTC)
The numbered editor was certainly overexcited, but s/he did point out that this article gave insufficient guidance as to where to find evidence for the statement about supernovae. In my teaching experience, one student who asks a question (even rudely) usually represents a number of others who wonder the same thing. So I thought it best to include a pointer to the more detailed discussion which DMacks had suggested above, in order to help future readers who may ask themselves the same question (hopefully more politely). I thought of a footnote first, but I accept RockMagnetist's correction to a Main article link, which is Wiki style for pointing to more detailed discussion of a (sub)section topic.
As for the restriction to radioactive primordial nuclei, we could say instead (or also) that all primordial nuclei heavier than iron (or nickel?) are from supernova explosions. This would go slightly outside the article topic, but also give more information very concisely.
Sorry, forgot to sign previous comment. Dirac66 (talk) 21:54, 20 December 2012 (UTC)
Thanks for the clarification. It never hurts to be clear. Sbharris, it's ironic you point to WP:SS because in Wikipedia:SS#References it says "Each article on Wikipedia must be able to stand alone as a self-contained unit (exceptions noted herein)." (I don't know what exceptions they are referring to.) It makes sense for each article to have its own citations because other articles can change - and actually Nucleosynthesis isn't particularly well provided with citations. I have never seen an inline citation described as a "waste of space" before. RockMagnetist (talk) 22:54, 20 December 2012 (UTC)
Come to think of it, an external citation doesn't even take up more space than the internal citation that I removed. RockMagnetist (talk) 23:00, 20 December 2012 (UTC)
I was thinking of internal space (what you see in edit mode) but never the less I'll admit you're right that cites are needed everyplace. Even summary sections with main articles need a cite or two. In an article like the United States (summarized by section as heavily as any you'll see) the standard seems to be about one cite per paragraph. So knock yourself out here, but it shouldn't take more than one or two on this particular point.

As to the more interesting question of where heavier-than-iron nuclides come from, it's complicated. About half of the nuclei heavier than iron are s-process nuclei that required some slow cooking somewhere (like AGB stars where free neutrons come from alpha reactions on C-13 and Ne-22) and the rest are r-process nuclides that require a truly titantic neutron flux from some fusion bomb event (like the first H-bombs making Es and Cf out of U and Pu). The sites for this are probably high mass supernovae that aren't quite large enough to make black holes, but have as many free neutrons at the end as possible. Certainly U and Th were made that way, and I'll have to go through the tables to see about the other 30-odd primordial radioactives. Some may be s-process nuclides that haven't been (or at least were not REQUIRED to have been) put through a genuine supernova or even nova, so we'd be liars if we said that all such nuclides heavier than iron had. Apparently red giants make some really heavy nuclides by the s-process, dreging them up and saute-ing them, then eventually puffing them gently out into space to make later generation solar systems like ours. SBHarris 06:02, 21 December 2012 (UTC)

Diagram Problem[edit]

The diagram that shows all the isotopes possible plotted on N vs Z is cool. The diagram just below it that shows how various decay modes transition within the former diagram is cool. what's not cool is that they have contradictory axes; the top diagram has N vertically while the bottom one has Z vertically. The two could make beautiful harmony, if only they could agree. Also, in the result transition diagram, there is a small epsilon associated with beta+, a positron. I've never seen that convention before. Am I just behind the nuclear physics joke curve?  :) SkoreKeep (talk) 06:31, 3 January 2013 (UTC)

Oops, pardon me. The transition diagram is just above, not below, the N/Z plot. — Preceding unsigned comment added by SkoreKeep (talkcontribs) 06:35, 3 January 2013 (UTC)

The lower complicated one is standard. It would be nice if somebody would make a version of the upper one showing transmutations, that had its axes flipped in the same direction. Perhaps you could write a note to the original maker?

The epsilon stands for a a separate process called electron capture that always competes with positron decay, requires less energy, and produces the same transmutation. SBHarris 08:35, 3 January 2013 (UTC)

I could do it (and notify the author)... M∧Ŝc2ħεИτlk 08:39, 3 January 2013 (UTC)
Done, any better? M∧Ŝc2ħεИτlk 08:46, 3 January 2013 (UTC)
I don't see it. Post it here, why don't you ? SBHarris 09:21, 3 January 2013 (UTC)

It was in the article and you only had to refresh, but here it is anyway:

Different types of decay of a radionuclide. Vertical: atomic number Z, Horizontal: neutron number N


M∧Ŝc2ħεИτlk 09:26, 3 January 2013 (UTC)

Wow I cannot get my browser to refresh. Do you know how without logging out? I even see the old version here on the talk page. I DO see the new one when clicking the photo itself and (yes) that's exactly what was needed. Thanks! SBHarris 19:25, 3 January 2013 (UTC)
...No problem, sorry about that. It should be possible to refresh anytime by clicking veiw -> refresh in the menu of the browser or ctrl+r (assuming Windows... not sure on Mac/Linux etc.) M∧Ŝc2ħεИτlk 20:14, 3 January 2013 (UTC)

Obscure symbol[edit]

Is the symbol ε standard? I have never seen it used to mean electron capture before and am more familiar with EC. Anyway ε is not defined in this article, neither in the caption to the figure discussed above, nor in the accompanying text, nor in the tables of different types of decay. Nor is it defined in the article on Electron capture. If we are going to use this symbol in the figure we must define it, but I think it would be simpler to just write out electron capture in the figure itself. Dirac66 (talk) 20:03, 3 January 2013 (UTC)

If it's ok I tweaked the caption of the image, I've never come across the epsilon notation for electron capture either... M∧Ŝc2ħεИτlk 20:14, 3 January 2013 (UTC)
I went ahead and changed "ε" to "EC" for short. Better? M∧Ŝc2ħεИτlk 20:25, 3 January 2013 (UTC)
Yes, EC is better, thank you. The only trouble is that like SBHarris, I only see the new image by clicking on the photo itself to go to the image file. In the article itself I still see the 2009 version with Z on the vertical axis and N horizontal, and refreshing my browser (IE8) does not seem to help. And I also tried Mozilla Firefox and still saw the 2009 version. Can there be a bug in the Wikipedia system for this image?? Dirac66 (talk) 21:58, 3 January 2013 (UTC)
That's really strange... I can see it perfectly... There can't be any internal bugs with the image (else it would not have uploaded). M∧Ŝc2ħεИτlk 22:06, 3 January 2013 (UTC)
I've notified the issue here, comments are welcome. Apologies, M∧Ŝc2ħεИτlk 22:23, 3 January 2013 (UTC)
Actually it depends where I look. I do see the new 2013 version at the top of the image file page File:Radioactive decay modes.svg, but on the article page Radioactive decay, I see the old 2009 version. And I have a PC, but I just got the same results on a Mac belonging to someone who would not have this image cached (because she never looks at physics articles). Dirac66 (talk) 22:45, 3 January 2013 (UTC)


Different types of decay of a radionuclide. Vertical: atomic number Z, Horizontal: neutron number N
Different types of decay of a radionuclide. Vertical: atomic number Z, Horizontal: neutron number N
LOL. Dirac66 has applied ye olde scientific method by using another computer and discovering that image cache-ing is indeed not the problem. I found that the image shows the newer version when simply displayed without the thumb box. From then on, it was a matter of applying controls to isolate the variables one-at-a-time. So, all you science dudes, what is the difference between the two images left and right? Don't look below, it's a puzzle.
An old name for K-capture is epsilon decay (which redirects to electron capture on WP), and if you google "electron capture epsilon" you get some interesting cases where the epsilon is used as a symbol for this decay. The German WP article on electron capture mentions this, but the English one does not.
Anyway, size matters. If your thumb box is just an episilon too small for the new fancy image, the computer will find an older version of the same image that WILL fit it. Apparently. That's my hypothesis, and I'm stickin' to it. SBHarris 03:31, 4 January 2013 (UTC)
Well, as long as its visible in the main article to everyone there's no problem. Thanks for clearing that up! M∧Ŝc2ħεИτlk 08:58, 4 January 2013 (UTC)
Yes, it works for me too now. Very good, and I will remember your hypothesis if I ever see the problem in another article. As for epsilon decay, I would guess this name was proposed after Thomson's delta rays, and that physicists later abandoned both letters for the more descriptive modern terms. Dirac66 (talk) 12:27, 4 January 2013 (UTC)

6He and 8He[edit]

Look at Isotopes of helium #Table: these isotopes appear to be able simultaneously emit a β and split to two nuclei: 6
2
He
 → 4
2
He
 + 2
1
D
 + e + ν
e
. This article does not know such type of decay. Incnis Mrsi (talk) 18:21, 1 February 2013 (UTC)

Exact probability distribution of N(t) when it is not assumed continuous[edit]

The article says:

"[...] Although the parent decay distribution follows an exponential, observations of decay times will be limited by a finite integer number of N atoms and follow Poisson statistics as a consequence of the random nature of the process. [...]"

I'm pretty sure that the exact distribution is not Poisson's; it is Binomial with parameters N_0 and e^{-\lambda \cdot t}. I have done the math derivation myself.

I added the "citation needed" template as a warning for readers.

GNU/Octave code to simulate problem: http://pastebin.com/UHsrfXu0 (comments in Spanish)

Generated image: http://postimg.org/image/dqe92tzkn/

(In the background you can see a 3D plot (with color) of the Binomial probability function (of N(t)) evolving with time)


 — Preceding unsigned comment added by Francisco Albani (talkcontribs) 08:02, 19 June 2013 (UTC) 
The discussion of Poisson statistics was confused. I have corrected it and added a citation. I think your calculation is reproducing the usual derivation of the exponential decay law by considering finite time intervals. RockMagnetist (talk) 14:23, 19 June 2013 (UTC)

Chain of two decays: 'the equation is not"[edit]

From the article:

\frac{\mathrm{d}N_B}{\mathrm{d}t} = - \lambda_B N_B,
adding the increasing (and correcting) term obtains the law for a decay chain for two nuclides:
\frac{\mathrm{d}N_B}{\mathrm{d}t} = -\lambda_B N_B + \lambda_A N_A.
The equation is not
\frac{\mathrm{d}N_B}{\mathrm{d}t} = - \left ( \lambda_B N_B + \lambda_A N_A \right ) ,
since this implies the number of atoms of B is only decreasing as time increases, which is not the case.

I don't think having incorrect equations in an article is a good idea: when people are looking for the formula, they won't pay much attention to the text, and even when they know the last one is wrong, they may accidentally copy it (easy mistake to make: you look up from your paper, see a line that begins with what you just wrote, so you assume that's the one you were copying). I doubt that people who know differential equations would need to be told explicitly why the two terms don't have the same sign, and you certainly don't need an incorrect formula to explain the correct one. Ssscienccce (talk) 19:14, 20 January 2014 (UTC)

I agree that incorrect equations are undesirable and can lead to confusion, so I will now remove the first of the above three equations (with one term only) and the third (with the wrong sign). The correct second equation is still explained very adequately. Dirac66 (talk) 23:58, 20 January 2014 (UTC)

Radioactive Dating Filed Under Wrong Heading[edit]

This text, which appears under the "Discovery and History" heading, should be moved to the "Occurrence and applications" section:

The discovery of radioactive elements in the 1890s opened the way for new dating techniques that suggested an age for Earth of several billion years.

That is, assuming it belongs in the article at all. There are numerous applications of radioactivity that are not listed anywhere in this article; Food irradiation, cancer treatment, tracing underground pipes, labeling chemicals for biological experiments, smoke detectors, radio-thermal generators,... That's just scratching the surface. There's no scientific reason why dating rocks and fossils is any more special than any of those. 129.42.208.183 (talk) 23:10, 30 January 2014 (UTC)

Concerning all the changes I made to the article[edit]

You are welcome. Zedshort (talk) 01:37, 30 September 2014 (UTC)