Factors which influence to half-life speed

[ansenko]

Looking for researches, articles and experimental values conserning factors which influence to half-life speed for different isotopes.

 

[mathman]

Half life refers to time not speed.

http://en.wikipedia.org/wiki/Radionuclide

 

[e.bar.goum]

In general, the halflife of an isotope is considered to be constant, providing physics doesn't change over time. ;)

The exception is decay via electron capture. That is changed by the amount of electrons in the vicinity of the decaying nucleus e.g. the charge state of the atom. For example, the half-life of completely ionized 7Be is infinite, as the only possible decay channel is EC. For most isotopes that decay via EC, it is only one of the possible decay channels.

 

[ansenko]

Until recently it was considered that, for example NaCl as an stable compounds is only possible.

Most of ordinary sources are in the scope. But it's not enough for our "data science" project. The idea is to build some hierarchy of conditions and measurement approach classes, then upload data with indication of accuracy class and test our data analysis model.

So we need really huge amount of data, not just consideration.

 

[ansenko]

Half life refers to time not speed.

http://en.wikipedia.org/wiki/Radionuclide

Please don't multiplied entities beyond necessity
http://en.wikipedia.org/wiki/Reaction_rate

 

[e.bar.goum]

Until recently it was considered that, for example NaCl as an stable compounds is only possible.

What has this got to do with nuclear physics? or half life?

http://en.wikipedia.org/wiki/Reaction_rate

What does this have to do with half-life?

Perhaps you need to reframe the question.

 

[ansenko]

Perhaps you need to reframe the question.

Ok. Can you give me the link to the researches (where described approaches and methods) and experimental data which prove all this values of half-life mentioned here: http://en.wikipedia.org/wiki/Radionuclide

 

[e.bar.goum]

Sure!

The National Nuclear Data Center is home to most of the collated knowledge of nuclear physics. It is home to the consensus values of half-lifes in the community. Now, if you want to go look at the half life of a particular nucleus, and see the original study, you want to go to the ENSDF database http://www.nndc.bnl.gov/ensdf/ and search for the isotope of interest. The ENDSF file will include the references to the experimental data. For example, I pick 14C, and get this page by selecting the adopted levels, gammas page (but you may also pick reaction by reaction if you choose) http://www.nndc.bnl.gov/useroutput/AR_B3250B5CB2E46AC0B6E43179706C2AB0_1.html

This tells me that the half life is 5700 years, and that this is found from:

T½: From the weighted average of the values 5780 y 65 [Watt et al. Intern. J. Appl. Radiat. Isot. 11 (1961) 68], 5680 y 40 (1962Ol04), 5745 y 50 (http://www.nndc.bnl.gov/nsr/nsrlink.jsp?1964Hu09,B ), 5660 y 30 (1968Be47), and 5736 y 56 (1968ReZZ and 1972Em01). The reduced-χ2 for this average is 1.06. These values were obtained from specific activity measurements. Values that have not been included in the average, all earlier, are 4700 y 400 (1946Re10), 5100 y 200 (1948No02), 7200 y 500 (1948Ya02), 6360 y 200 (1949Ha52), 5589 y 75 (1949Jo07), 5580 y 90 [Engelkemeir & Libby, Rev. Sci. Instr. 21 (1950) 550], 6360 y 190 and 5513 y 165 [Miller et al., Phys. Rev. 77 (1950) 714], 5370 y 200 [Manov & Curtiss, J. Research Nat. Bur. Std. 46 (1951) 328], 6100 y 85 (http://www.nndc.bnl.gov/nsr/nsrlink.jsp?1952Je11,B ), 5900 y 250 [Caswell et al., J. Research Nat. Bur. Std. 53 (1954) 27]. These values were omitted because of their large uncertainties and the later improvements in the measurement methods. From a similar evaluation, 1990Ho28 gives a result of 5715 y 30 from an unweighted average of eight values. Evaluated by V. Chechev in 1998 in conjunction with the Decay Data Evaluation Project (1999BeZS,1999BeZQ).

And I could go look at those papers now, and see the experimental methods used.

Hope this helps!

 

[ansenko]

Great! Thanks a lot!

 

[ansenko]

Going to add some related links in this tread:
1. Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance
http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.3283v1.pdf
2. Evidence against correlations between nuclear decay rates and Earth–Sun distance
http://donuts.berkeley.edu/papers/EarthSun.pdf
3. Experiments on the Effect of Atomic Electrons on the Decay Constant of Be7 II.
https://publications.lbl.gov/islandora/object/ir%3A147066
4.PERTURBATION OF NUCLEAR DECAY RATES
http://www.whoi.edu/cms/files/1972AnRevNucSci22p165_68424.pdf

 

[Vagn]

Going to add some related links in this tread:
1. Evidence for Correlations Between Nuclear Decay Rates and Earth-Sun Distance
http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.3283v1.pdf

The findings of that paper were later discussed here which found no such variation in other data sets.
See here also.