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Pairing effects

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The primordial nuclide total listed here (289) does not match that given elsewhere in wikipedia i.e. at Primordial Nuclide (288). The EE value there is 169. I think that U-234 was accidently included here. The next long lived nuclide after Pu-244 (82My) is Nb-92 (37My). This should be the 289th primordial nuclide. U-235 has only a 245ky half life. The tables at the start and end of the article also need fixed to show 288 total primordial nuclides. 99.32.172.114 (talk) 05:23, 14 April 2013 (UTC)[reply]

Fissile nuclides

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Fissile nuclides tend to have even Z and odd N. This is very important and should perhaps be more prominently stated in the article.

Looking for better sources. Andrewa (talk) 04:07, 6 February 2024 (UTC)[reply]

I believe that they can also have odd Z, but those tend to have shorter half-life. But yes, odd N, and the article should explain that. It is the extra binding energy of paired neutrons that does it. Gah4 (talk) 06:42, 6 February 2024 (UTC)[reply]
Interesting... what would be an example of a fissile nuclide with odd Z? Andrewa (talk) 07:15, 6 February 2024 (UTC)[reply]
It appears that the odd-odd neptunium-236 is fissile, and not only fissionable. See page 13 of [1]. Complex/Rational 18:35, 6 February 2024 (UTC)[reply]
Interesting... that's the source given here too. That document doesn't seem to cite the source of its information, and the document as a whole is a very deliberately conservative evaluation. Can we do better, I wonder? Andrewa (talk) 19:46, 12 February 2024 (UTC)[reply]
@Andrewa: I found some more about it (and fissile nuclides in general) in doi:10.1119/1.4966630 – the key takeaway is that 236Np is fissile, but so difficult to produce that its critical mass has not been experimentally measured. It also clearly states that even-N nuclides such as 237Np and 241Am are not fissile, despite other sources categorizing them as such. I can email you a pdf of the article if you can't access it online. Complex/Rational 23:44, 12 February 2024 (UTC)[reply]

Odd-odd nuclides that are very stable to beta decay and/or IT

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For some odd-odd nuclides, beta decay and/or IT requires high spin change. For the following nuclides, a such decay process is at least 3 forbidden non-unique or 4 forbidden unique. The states are taken from:

https://www.nndc.bnl.gov/nudat3/getdataset.jsp?nucleus=X&unc=NDS, where X is a nuclide symbol (for example https://www.nndc.bnl.gov/nudat3/getdataset.jsp?nucleus=50V&unc=NDS);

If the link does not work, an alternative is

https://www.nndc.bnl.gov/ensnds/M/X/adopted.pdf, where X is an element name and M is a mass number (for example https://www.nndc.bnl.gov/ensnds/50/V/adopted.pdf).

Nuclide QITmax (keV) QECmax (keV) Qβ−max (keV) Possible IT processes Possible EC processes Possible β− processes
50V - 2204.9 1037.9 - 6+→0+JΔπ = 6+), 2204.9
6+→2+JΔπ = 4+), 651.1
6+→0+JΔπ = 6+), 1037.9
6+→2+JΔπ = 4+), 254.6
180mTa 77.2 929.4 785.5 9→1+JΔπ = 8), 77.2
9→2+JΔπ = 7), 37.7
9→0+JΔπ = 9), 929.4
9→2+JΔπ = 7), 837.0
9→4+JΔπ = 5), 620.8
9→6+JΔπ = 3), 288.6
9→0+JΔπ = 9), 785.5
9→2+JΔπ = 7), 681.9
9→4+JΔπ = 5), 447.9
9→6+JΔπ = 3), 97.0
210mBi 271.3 207.8 1432.6 9→1JΔπ = 8+), 271.3
9→0JΔπ = 9+), 224.8
9→0+JΔπ = 9), 207.8 9→0+JΔπ = 9), 1432.6
9→2+JΔπ = 7), 251.2
9→4+JΔπ = 5), 5.9
214mAt 231.0 1321.4 1170.9 9→1JΔπ = 8+), 231.0
9→0JΔπ = 9+), 153.0
9→2JΔπ = 7+), 85.9
9→3JΔπ = 6+), 44.0
9→4JΔπ = 5+), 2.9
9→0+JΔπ = 9), 1321.4
9→2+JΔπ = 7), 712.1
9→4+JΔπ = 5), 306.3
9→3JΔπ = 6+), 46.6
9→0+JΔπ = 9), 1170.9
9→2+JΔπ = 7), 476.1
9→4+JΔπ = 5), 29.7

103.166.228.86 (talk) 15:29, 15 April 2024 (UTC)[reply]

Note that the spins of 180Hf and 180W are also due to collective nuclear rotation. 14.52.231.91 (talk) 00:56, 20 August 2024 (UTC)[reply]

Beta decays of odd-odd nuclides with low spin change that take a long time to happen

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Look at the level diagram (in keV) of some decay products:

Nuclide 0+ → 2+ 2+ → 4+ 4+ → 6+ 6+ → 8+ 8+ → 10+ 10+ → 12+ 12+ → 14+
176Hf 88.35 201.83 306.64 400.91 483.33 553.60 611.94
236U 45.24 104.24 160.31 212.47 260.14 303.00 341.00
236Pu 44.6 102.8 158.4 209.9 257.8 300.8 339.3
248Cm 43.4 100.4 155.1 207.5 256.4 301.3 342.1
248Cf 41.5 96.3 149.6 200.6 249.5

These levels are separated by units of spin, and their energies get further apart as the spin increases. That's a classic sign of collective nuclear rotation, with a rigid rotor having kinetic energy . On the other hand, the high spins of 176Lu, 236Np, and 248Bk are intrinsic, so the decay processes must overcome a terrible match even if the spin change is low. Their β decay information:

Decay process Qβ (keV) Spin change Half-life (a) Intensities taken from
176Lu → 176Hf 593.33 7 → 6+JΔπ = 1, 1 forbidden non-unique) 3.72×1010 [2]
192.49 7 → 8+JΔπ = 1, 1 forbidden non-unique) 9.49×1012
236Np → 236U 783.52 6 → 4+JΔπ = 2, 1 forbidden unique) unknown (at the order of 108?) [3]
623.21 6 → 6+JΔπ = 0, 1 forbidden non-unique) 1.78×105
85.40 6 → 5JΔπ = 1+, allowed) 1.55×108
236Np → 236Pu 329.15 6 → 4+JΔπ = 2, 1 forbidden unique) unknown (at the order of 109?) [4]
170.80 6 → 6+JΔπ = 0, 1 forbidden non-unique) 1.29×106
248Bk → 248Cm 388.07 6+ → 6+JΔπ = 0+, allowed) unknown (at the order of 107?)
248Bk → 248Cf 552.01 6+ → 6+JΔπ = 0+, allowed) unknown (at the order of 106?)

On the other hand, the longevity is probably not applicable to the unknown decay processes 212mAt → 212Po (9 → 8+, QEC = 271.84 keV) and 216mAt → 216Rn (9 → 8+, Qβ− = 517.68 keV), because the high spin of 212Po and 216Rn does not seem to be a result of collective nuclear rotation, as their level diagrams are irregular:

Nuclide 0+ → 2+ 2+ → 4+ 4+ → 6+ 6+ → 8+ 8+ → 10+ 10+ → 12+ 12+ → 14+
212Po 727.33 405.18 222.98 120.90 357.50 868.34 183.17
216Rn 461.4 379.1 385.4 419.1 294.7 465.9 420.5

It should be pointed out that, although not specified, it seems that 212mBi → 212Po (9 → 8+, Qβ− = 775.11 keV) is known, as shown in the last diagram of here. 129.104.241.193 (talk) 15:10, 7 May 2024 (UTC)[reply]

According to here, collective nuclear rotation of even-even nuclides is being charateristic of having transition energies , where is the mass number, is the spin and is a constant about . This matches the first table above in this section extremely well. We can also see that the spins of states of 212Po or 216Rn are by no means due to collective nuclear rotation.
According to the same link above, collective nuclear rotation is typical for nuclides with or . 14.52.231.91 (talk) 07:20, 15 August 2024 (UTC)[reply]
Other than 176Lu, 236Np, 248Bk, lack of beta decay of 186mRe and 242mAm (but their IT decays are known in contrast to the former three nuclides) is also due to collective nuclear rotation of beta daughters (186Os, 242Pu/242Cm). 14.52.231.91 (talk) 00:22, 16 August 2024 (UTC)[reply]
Well I'm not quite sure about 186mRe. In theory the only available beta process should be 186mRe (8+) → 186Os (6+), Q = 149.93 keV. This is itself a 2 forbidden non-unique process with a relative small decay energy. And considering that the similar process 98Tc (6+) → 98Mo (4+) (where the 4+ spin of 98Mo is not due to collective nuclear rotation), Q = 173.95 keV is not even known... 14.52.231.91 (talk) 02:04, 16 August 2024 (UTC)[reply]
Also, it is worthy noting that the transition energies of 186W and 186Os still satisfy , but here is about , about 1.7 times compared to other even-even nuclides considered above. Are there any explanations? 14.52.231.91 (talk) 02:14, 16 August 2024 (UTC)[reply]

Odd-odd isomers

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Many odd-odd nuclides have a low-spin state and a high-spin state whose energies are close to each other. For these nuclides, IT of the state with higher energy is pratically impossible, so the two states behave somehow like "two ground states". Here are some examples.

Nuclide Low-spin state High-spin state
92Nb 2+ (135.5 keV, β+=10.15 d, β-=?) 7+ (0 keV, EC=3.47×107 y, β-=6.94×1010 y)
166Ho 0- (0 keV, β-=26.824 h) 7- (5.985 keV, β-=1.20×103 y)
176Lu 1- (122.845 keV, β-=3.667 h, EC=160.7 d) 7- (0 keV, β-=3.701×1010 y, EC=8.22×1012 y)
180Ta 1+ (0 keV, EC=9.593 h, β-=2.265 d) 9- (77.1 keV, EC=very long, β-=very long)
248Bk 1- (order uncertain, β-=1.41 d, EC=3.29 d) 6+ (order uncertain, β-=?, EC=?)

Note that this list does not include 186Re or 242Am, because the ITs of their isomers are well known. — Preceding unsigned comment added by 103.166.228.86 (talk) 00:59, 12 September 2024 (UTC)[reply]