Talk:Isotopes of tantalum

meta-stable tantalum
Hey, I'd love to read more about these nuclear isomers - especially now that I know I actually own an extremely small quantity of the stuff - in capacitors, of course! I remember feeling pretty amazed when I first read about it not that long ago; even more surprised when I found out that the discovery was much longer ago (I guess it didn't make the news... ) Zaphraud (talk) 05:18, 25 March 2011 (UTC)

Why is Ta-180m so stable?
Can someone add an explanation of why this nuclear isomer (or excited state) is so stable? I would guess that predicted to decay merely means here that the 3 decay modes are calculated to be exoenergetic, but that each one would violate some strong selection rule(s). Can someone point to a reference which says so and explains in more detail? Dirac66 (talk) 20:26, 13 August 2012 (UTC)
 * You can look at this. It says mostly what we've said. The problem with Ta-180 is that the 180m state is only the third excited state. The two below it have spins of +1 and +2, whereas the 180m state is -9 with this huge spin. It needs to get rid of at least 7 units of spin in a single decay, and 8 to get to the ground state. That makes it 5th-forbidden for beta decay (which could go positron or electron, since it's odd-odd), and in gamma decay, you get a factor of 10^5 in extra lifetime for every unit of angular momentum greater than 1. So we've got to emit one photon with at least 7 units more than that, which takes 10^35 times the lifetime of the 10^-12 sec for a usual gamma decay, which gives 10^23 sec or (ta-dah!) 10^15 years. If use that rule of thumb for Tc-99m, you find it need to change spin by 4 in a gamma decay, and thus is inhibited by an extra spin of 3 over the minimum 1. Multiply 10^-12 by (10^5)^3 = 10^15 and obtain a life time of 1000 seconds or 17 minutes, which isn't all that far from the observed 6 hours. So this all makes a sort of sense. Halfnium-178m3 with the half life of 31 years or so has a spin of 16. However, I don't think it is as inhibited as Ta-180m because (unlike Ta-180m), Hf-178m3 has some intermediate-energy states to decay to (some of them NOT metastable, so you don't seem them in metastable lists). I infer that the nearest of these has a delta-J of 5 which is 4 units inhibited, and that gives you the extra lifetime of 100,000 times that of Tc-99m. Which would be 6 hours times 10^5 = 68 years. Close enough. S  B Harris 22:13, 13 August 2012 (UTC)
 * Thanks. Qualitatively as I thought, but I hadn't known how to do the quantitative estimates which are quite interesting. I see that you have now also expanded the explanation at Isotope.
 * I will add the van Dommelen link as a reference. Also I will change the phrase is predicted to decay in three ways to has sufficient energy to decay in three ways, in order to avoid suggesting that it is predicted to decay at an observable rate. Dirac66 (talk) 20:29, 22 August 2012 (UTC)

Ta180m
I can't find a mechanism for creating Ta180m, why does any exist? And what is the mechanism?32ieww (talk) 02:42, 25 February 2017 (UTC) 32ieww (talk) 02:42, 25 February 2017 (UTC)

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"Rarest isotope" listed at Redirects for discussion
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Alpha decay of Tantalum-180m
If I've calculated correctly, Tantalum-180m is also energetically capable of alpha decay into Lutetium-176, another primordial isotope. That would only require the loss of two units of spin through gamma rays. Is there a reason this is forbidden? 2600:8803:B102:F900:ECB7:DA58:A0D2:99A4 (talk) 22:54, 20 August 2023 (UTC)


 * In theory, all stable nuclides with mass ≥ 142, other than 142,150Nd, 144,154Sm, 156,157,158,160Gd, 159Tb, 163,164Dy and 204Hg, are energetically allowed to undergo alpha decay. But the theory is just the theory: many of them also have much too long half-life in theory! According to, only 149Sm and 187Os have theorized half-life less than 1020 years among those that are observationally stable, so one could expect that they are the only candidates yet to be found to undergo alpha decay. As one can see, then theorized alpha decay half-life of 180mTa is at the order of 1026 years. 129.104.241.214 (talk) 22:27, 9 November 2023 (UTC)

Possible alpha decay of 155Ta and 156Ta
According to, 156Ta should have a partial alpha decay half-life at the order of 103 seconds, corresponding to a probability at the order of 0.01%.

155Ta has similar decay energy as 167Ta, so its alpha decay half-life could be at the order of 103 years, corresponding to a probability at the order of 10-12%. 129.104.241.214 (talk) 21:10, 28 January 2024 (UTC)

Request
This request was placed in the article. I've moved it here because this is the place for questions/comments/etc. about the article. From User:SalvageInsaneeeee: NOTICE: Tantalum-180m is supposed to say 1.44x10^27 years, i just suck at wikitext also remove this when someone fixes my wikitext problem. Joyous! Noise! 23:47, 24 February 2024 (UTC)


 * If 180mTa has indeed that half-life then there would be almost no hope detecting the radioactivity. I would guess that this is just a prediction. 129.104.241.218 (talk) 08:38, 10 April 2024 (UTC)

Stability of 180mTa
"The very slow decay of 180mTa is attributed to its high spin (9 units) and the low spin of lower-lying states." Does the high spin of 180mTa really explain its stability? 212mBi also have a spin of 9−, but it's β− decay half-life is only 76 min. 129.104.241.218 (talk) 21:42, 11 April 2024 (UTC)


 * 212Po has 8+ and (8-) excited state where 212mBi can conveniently decays to. Nucleus hydro elemon (talk) 12:02, 12 April 2024 (UTC)
 * Thanks! 23.165.104.101 (talk) 10:20, 15 April 2024 (UTC)
 * By the way, the same argument does not apply to 176Lu: the 7- spin of 176Lu is intrinsic, while the 6+ spin of 176Hf is due to collective nuclear rotation, as indicated by the $$E\propto J^2$$ relation for some states of 176Lu: see here for the states of 176Lu, and this PSE question for an explanation.
 * The same situation may apply to 248Bk (6-), which in theory can undergo EC decay to the 6+ state of 248Cm with Q value 391.3 keV, or β− decay to the 6+ state of 248Cf with Q value 557.6 keV. But the $$E\propto J^2$$ relation for some states of 248Cm or 248Cf means that the spins are due to collective nuclear rotation, while the spin of 248Bk is intrinsic. 129.104.241.193 (talk) 15:28, 4 May 2024 (UTC)