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Author Topic: three curves of stability?  (Read 4833 times)

Offline ghh

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three curves of stability?
« on: 11/06/2008 14:50:52 »
Has anyone come accross this?


 

lyner

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three curves of stability?
« Reply #1 on: 11/06/2008 22:01:07 »
Hi ghh.

Too hard for me, Guv.
You might like to try a more 'meaty' Physics forum. There are quite a few on the Web.
 

Offline Soul Surfer

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three curves of stability?
« Reply #2 on: 11/06/2008 23:19:41 »
Yes it's simple enough.  A similar odd even and divide by four effect is also seen if you look at the number of stable isotopes elements have.  It is part of the vague nuclear shell structure.  The Helium4 nucleus seems also to be associated with this.  it is quite likely that helium nuclei can exist on the surface of a nucleus and are much easier to break off.  Much radioactivity involves the ejection of helium nucleii (alpha particles) rather than single protons or duterons.
 

Offline Bored chemist

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three curves of stability?
« Reply #3 on: 12/06/2008 19:28:22 »
A crassly unhelpful asnwer is that ghh has come across them. I seem to remember something about nuclear stability and odd/ even mass and z.

ghh, what do you want to know about them?
 

Offline ghh

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three curves of stability?
« Reply #4 on: 13/06/2008 18:29:39 »
I copied all the isotope tables from Wikipedia, and periodictable.com into one file so I could analyse the data. Its 2.8MB so too big to attach, but you can have a copy if you ask. I was going to attach the “missing bit” from the previous posting, but the pdf is too big, and it wont let me attach a doc. Here is a summary of the findings.
•   I have taken the 2,606 isotopes up to Atomic number 208, and sorted them by decay mode. Of these only 194 are fully stable and  2,173 are beta decays
•   There is only one fully stable “Z” isotope for a given atomic number “A”.
•   There are no stable isotopes above 208Pb. For any given Atomic number, most decays are either beta minus resulting in an increase in the Z number, or beta plus (or electron capture)resulting in a decrease in the Z number both converging on the unique Z number for the stable A number.
•   2Bminus and 2Bplus decays are from semi-stable long half life Isotopes, which always result in the stable Z of that atomic number. This is always accompanied by a single beta decay from the Z+/- 1 isotope.
•   All other decays are either to isotopes in another “A” number B chain or directly to other stable isotopes.
•   Bminus and Bplus decay chains are not symmetrical
•   The pattern of decay energies is different for Fermions and Bosons.
•   The “curve of stability” can be split into 3, one for fermions, one for boson numbers divisible by 4, and one for other even numbers.

Which gives rise to some questions

•   Bminus and Bplus decay chains are not symmetrical. Question  - electrons and positrons are supposed to be identical with opposite charge and spin. The data suggests there is a subtle difference in the way they behave in decay?
•   Nuclei have two classes: Fermions with fractional spins, and Bosons with 0 or whole number spins. The pattern of decay energies is different for Fermions and Bosons, but analysis shows that the Bosons have two classes, Atomic numbers divisible by 4, and other even numbers, leading to three “curves of stability”. Is this significant?
•   Where there is more than one isotope with the same Z number, it seems difficult to identify the difference apart from the mass. Is there an identifiable difference eg in the crystal structure, and /or in the spectral signature?
There may be more questions, but I haven’t finished stirring the data.
Graham
 

Offline Bored chemist

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three curves of stability?
« Reply #5 on: 14/06/2008 15:26:03 »
Are you sure about this "There is only one fully stable “Z” isotope for a given atomic number “A”.
"
Some elements have a hatfull of stable isotopes. Tin, IIRC has lots.
electrons and positrons are identical apart from their charge. But they are leaving the + charged nucleus which means the  chrage is very imprtant to how they act.

The differences between stable isotopes are generally rather small. They form identical crystals (apart from very small differences in some of the bond lengths. The spectra are generally very similar. The clear exception being any nuclear spectrum like NMR.
 

Offline ghh

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three curves of stability?
« Reply #6 on: 14/06/2008 16:51:38 »
Quote
author=Bored chemist link=topic=15054.msg179167#msg179167 date=1213453563]
Are you sure about this "There is only one fully stable “Z” isotope for a given atomic number “A”.

Yes. The A number the total number of nucleons. You will need my 2mb analysis file for the proof.
I have worked out how to attach the missing bit but it has to be in three posts, here is part 1
 
 

Offline ghh

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three curves of stability?
« Reply #7 on: 14/06/2008 16:52:48 »
part 2
 

Offline ghh

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three curves of stability?
« Reply #8 on: 14/06/2008 16:55:34 »
part 3.

These show the "beta decay well" effect for stable Isotopes.

When you have read I will need to talk to you about
Quote
author=Bored chemist link=topic=15054.msg179167#msg179167 date=1213453563]The clear exception being any nuclear spectrum like NMR.
 

Offline Bored chemist

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three curves of stability?
« Reply #9 on: 14/06/2008 20:59:10 »
I'm still not sure what you mean.
Look at tin as an example. It has stable isotopes with masses of 114,114,115,116,117,118,119,120,122 and 125 (If my trusty copy of the Merck index is to be believed).
Same atomic number (ie Z) but different numbers of neutrons.

Tellurium has stable isotopes with masses 120,122,123,124,125,126,128 and 130
Again same Z but differnt masses.
But 122 Sn and 122Te both have 122 neucleons in total.
Similarly with 125Sn and 125Te.
The two pairs have the same value for A
The same goes for 40Ca and 40Ar (these 2 are the lightest isobaric pair I think.)



 

Offline ghh

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three curves of stability?
« Reply #10 on: 15/06/2008 17:10:11 »
(If my trusty copy of the Merck index is to be believed).

Ah! Wiki also has these as stable but Periodictable.com has more data.
For 114,115,116,117,118,119,120 the only stable Z number is 50Sn.

122, Z50 has a 2b- 368.08keV decay to 122/52Te which is the only stable Z for 122.
http://periodictable.com/Isotopes/050.122/index.p.full.dm.html [nofollow]

125Sn is a B- 2356.97keV to 125Sb then B- 766.7keV to 125/52Te which is the only stable Z for 125.
I think you meant 124, where Z 50 has a 2B-  2287.8keV decay to 124/52Te which is the only stable Z for 124.

The solutions for Te are as follows

120 2b+ -343.91keV to 120Sn
122 STABLE
123  e (electron capture) 52.22keV TO 123Sb
124 STABLE
125 STABLE
126 STABLE
128 2B- 867.95keV to 128Xe
130 2B- 2530.3keV to  130Xe

40Ca is 2B+ -1850.78keV to 40 Ar Stable

The data sheets just will not reduce enough for me to attach.
 

Offline Bored chemist

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three curves of stability?
« Reply #11 on: 15/06/2008 19:26:09 »
Apart from that table is there any experimental evidence for double positron emision for 40Ca?
 

Offline ghh

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three curves of stability?
« Reply #12 on: 16/06/2008 10:14:23 »
Apart from that table is there any experimental evidence for double positron emision for 40Ca?
I would't know. I have just analysed the published data, found some correlations, which is why the questions. Its not just 40Ca. these 2beta decays eliminate all the doubles and triplets. These have very long half lives, so for practical chemistry purposes these are hardly relevant. But for nuclear theory it could be very significant.
Graham
 

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three curves of stability?
« Reply #12 on: 16/06/2008 10:14:23 »

 

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