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Element 117 Synthesized

  1. Apr 6, 2010 #1
    Element 117 has been synthesized:

    http://www.nytimes.com/2010/04/07/science/07element.html

    If the Island of Stability exists, and significant quantities of a stable element 126 could be synthesized, then what would be the practical applications of such a material?

    Could it be used for some kind of superior nuclear shielding, because of a larger nuclear cross-sectional area? Or could it instead be used as a high-energy density material?

    What are the likely useful properties of an hypothesized element 126?
     
  2. jcsd
  3. Apr 6, 2010 #2

    The nuclear reaction required to synthesize element 126 is impractical and at best could only produce a few short-lived nuclei for theoretical nuclear structure studies.

    Negative and negative.

    Only for the study of theoretical nuclear structure and studying the peak of the island of stability.

    Reference:
    http://en.wikipedia.org/wiki/Island_of_stability" [Broken]
    http://en.wikipedia.org/wiki/Ununseptium" [Broken]
    http://en.wikipedia.org/wiki/Unbihexium" [Broken]
     
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  4. Apr 7, 2010 #3
    I'd read that the estimated half-life of element 126 would be billions of years.

    So why do you feel it would be short-lived?

    If 126 has a complete shell, then why would it be unstable?
     
  5. Apr 7, 2010 #4
    I would be interested to read more details about this estimation.
     
  6. Apr 7, 2010 #5

    Astronuc

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    from http://pubs.acs.org/cen/news/84/i10/8410notw9.html [Broken]
    Element 126 (Z=126, N = 184, A = 310)
    As-yet-unsynthesized superheavy atom should form a stable diatomic molecule with fluorine

    I don't believe it's stability will be on the order of a billion years, but expectations are that it will be around long enough to measure chemical properties. That could mean hrs, minutes, maybe seconds. It would be dense, and would make a great shield for gamma and beta radiation, but it would likely be very unstable with respect to neutron absorption.
     
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  7. Apr 7, 2010 #6
    But if element 126 were to be found to be stable for some usefully long period of time, so that practical use could be made of it, then perhaps it could offer some invaluably unique properties.

    As mentioned, if it can absorb/block EM radiation, then that might make it useful for radiation shielding. However its high mass-density might keep it suitable only for stationary applications.

    But in relation to instability wrt neutron absorption, then maybe that might again make it useful as a power supply, or even just as a neutron detector. Maybe it would have a very low critical mass, so that you could take tiny powdered grains of the stuff and feed them to a neutron source, which would release lots of energy on demand.
     
  8. Apr 7, 2010 #7
    You must have read this "billions of years" somewhere. Would you care to answer where you read it, whether you forgot where you read it, or whether you just made it up ?

    Many application can be thought of for sure. There is a fundamental instability around Z ~ 180-200 however.
     
  9. Apr 7, 2010 #8

    bcrowell

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    First off, it depends on what isotope you're talking about. The best island of (relative) stability is predicted to lie at (N,Z) combinations that can't be created with the available beam-target combinations.

    In any case, I don't think there's ever been any modern prediction that anything in this region would have half-lives of billions of years. Hours would be impressive.

    Having a complete shell doesn't make a nucleus absolutely stable, it just makes it more stable than a nearby open-shell nucleus. All high-Z nuclei are unstable with respect to alpha decay and/or fission, and this is because the repulsive Coulomb interaction scales like Z^2.

    The only application I've ever heard proposed half-way seriously would be that if you could make a macroscopic quantity of an element from the island of stability (which you won't be able to do with any foreseeable technology), and if the half-life was long enough to be able to work with the stuff (which I don't think it would be), then you could make nuclear bombs the size of a pencil eraser.
     
  10. Apr 7, 2010 #9

    Astronuc

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    Considering what it takes to make element-126, I don't this material being practical, unless it is the only material that can perform some dramatic function. It certainly would not be a practical energy source for terrestrial applications.

    Metals block EM. Lead is ideal because it's cheap, and the cheaper the material the better.

    We have neutron detectors that work fine.

    I'm not sure that it's half-life will be long.
     
  11. Apr 7, 2010 #10
    theoretical and known nuclear half-lives...


    I pulled the half-lives for the theoretical isotopes mentioned by Glenn T. Seaborg and described in Wikipedia reference 1, and from the Moller Theoretical Nuclear Chart 1997 listed in reference 2.

    Possible magic number of neutrons for spherical nuclei:
    [tex](n_n,n_p)[/tex]
    [tex](184,114) \; \; \; ^{298}_{114} \text{Uuq} \; \; \; T_{1/2} = 1.2 \; \text{h}[/tex]
    [tex](184,120) \; \; \; ^{304}_{120} \text{Ubn} \; \; \; T_{1/2} = 150 \; \text{ns}[/tex]
    [tex](184,126) \; \; \; ^{310}_{126} \text{Ubh} \; \; \; T_{1/2} = 21 \; \text{ps}[/tex] - doubly magic
    [tex](126,82) \; \; \; ^{208}_{82} \text{Pb} \; \; \; T_{1/2} = \text{stable}[/tex] - doubly magic

    Isotopes of elements in the range between 110 through 114 have been found to decay more slowly than isotopes of nuclei nearby in the periodic table.

    Longest lived measured isotope in range 110 through 114:
    [tex](173,112) \; \; \; ^{285}_{112} \text{Cn} \; \; \; T_{1/2} = 29 \; \text{s}[/tex]
    [tex](173,112) \; \; \; ^{285}_{112} \text{Cn} \; \; \; T_{1/2} = 10 \; \text{h}[/tex] - theoretical

    Recent research indicates that large nuclei are deformed, causing magic numbers to shift. Hassium-270 is now believed to be doubly-magic nucleus, with deformed magic numbers 108 and 162. Its_half-life may be as high as 23 seconds.

    [tex](161,108) \; \; \; ^{269}_{108} \text{Hs} \; \; \; T_{1/2} = 9.7 \; \text{s}[/tex] - doubly magic
    [tex](162,108) \; \; \; ^{270}_{108} \text{Hs} \; \; \; T_{1/2} = 3.6 \; \text{s}[/tex] - doubly magic
    [tex](169,108) \; \; \; ^{277}_{108} \text{Hs} \; \; \; T_{1/2} = 16.5 \; \text{m}[/tex] - spontaneous fission

    The nucleus with Z=110, N=183 appears to be near the center of a possible 'magic island':
    [tex](183,110) \; \; \; ^{293}_{110} \text{Ds} \; \; \; T_{1/2} = 160 \; \text{d}[/tex] - magic island center
    [tex](184,110) \; \; \; ^{294}_{110} \text{Ds} \; \; \; T_{1/2} = 130 \; \text{y}[/tex] - magic island center

    [tex](171,110) \; \; \; ^{281}_{110} \text{Ds} \; \; \; T_{1/2} = 11 \; \text{s}[/tex] - spontaneous fission
    [tex](171,110) \; \; \; ^{281}_{110} \text{Ds} \; \; \; T_{1/2} = 9 \; \text{h}[/tex] - theoretical

    Longest lived theoretical chart isotope of Ubh:
    [tex](213,126) \; \; \; ^{339}_{126} \text{Ubh} \; \; \; T_{1/2} = 130 \; \text{y}[/tex]

    However note that the theoretical nuclear chart in this region is incomplete.

    Also note that the actual measured_half-life values are much less than those based upon the Moller theoretical model, and are therefore a theoretical upper limit.

    Reference:
    http://en.wikipedia.org/wiki/Island_of_stability" [Broken]
    http://ie.lbl.gov/toipdf/theory.pdf"
    http://en.wikipedia.org/wiki/Hassium" [Broken]
    http://en.wikipedia.org/wiki/Darmstadtium" [Broken]
     
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  12. Apr 8, 2010 #11
    Probability that Z=117 becomes Ignobelum is now > 0. My greatest contribution to science to-date (I'm getting there!).
     
  13. Apr 9, 2010 #12
    Here's another brief article that may be of interest, from the APS online publication Physics: http://physics.aps.org/articles/v3/31" [Broken].
     
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  14. Apr 9, 2010 #13

    bcrowell

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    That was an excellent article -- thanks for posting the link!

    I hadn't realized that odd-odd nuclei could have such strong hindrance factors against spontaneous fission. The physical reasons for this aren't obvious to me. Does anyone understand this?
     
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  15. Apr 10, 2010 #14
    Spontaneous fission...


    The primary factors for spontaneous fission is nuclear deformation and available nuclear shell energy. This is also true for any nuclear fission reaction.

    The odd-odd nuclei can still have a degree of spherical symmetry with insufficient shell energy for a spontaneous fission reaction.

    Spontaneous fission occurs due to quantum tunneling, without the nucleus having been struck by a neutron or other particle as in induced nuclear fission.

    Reference:
    http://en.wikipedia.org/wiki/User:ANUnuclearhonoursclass/Nuclear_Deformations" [Broken]
    http://en.wikipedia.org/wiki/Spontaneous_fission" [Broken]
    http://en.wikipedia.org/wiki/Quantum_tunneling" [Broken]
     
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  16. Apr 10, 2010 #15

    Astronuc

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    From the APS/PRL article - http://physics.aps.org/pdf/10.1103/PhysRevLett.104.142502.pdf [Broken]
    "The cross sections for producing the nuclei of element 117 in the reaction 249Bk + 48Ca are σ = 0.5 (+1.1,-0.4) pb and σ = 1.3(+1.5,-0.6) pb at E* = 35 MeV and E* = 39 MeV, respectively. These values are similar to the results of previous experiments where cross sections for the reactions of 233;238U, 237Np, 242;244Pu, 243Am, 245;248Cm, and 249Cf targets with 48Ca beams have been measured [1]."

    1. Yu. Ts. Oganessian et al., J. Phys. G 34, R165 (2007), and earlier references therein.

    E* = excitation energy

    Given the extremely small cross-section on the order of pb (pico-barns), the creation of superheavy elements cannot be practical for energy storage or other useful applications.

    I would imagine that the propensity for spherical symmetry would coincide with the low probability for spontaneous fission.
     
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  17. Apr 10, 2010 #16

    bcrowell

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    Re: Spontaneous fission...

    This is correct.

    Sure. What I think you're describing here is the standard picture in which you have a potential energy landscape as a function of deformation. The total potential energy is usually determined by taking a liquid-drop term plus a shell correction, the shell correction being calculated by the Strutinsky smearing technique.

    I don't think this is correct. Typically adding unpaired nucleons does not have any dramatic effect on the shape of the nucleus.

    I don't think this is correct either. Typically the way one would calculate this would be:
    [tex]E_{LD}+E_S+E_p[/tex] ,
    where E_LD is the liquid drop energy, E_S is the Strutinsky smearing correction, and E_p is a pairing energy. By "shell energy," I assume you mean something like E_S; this does not generally change drastically just because you add an odd nucleon. The main effect of adding the odd nucleon would be in the E_p term, which basically gives an extra energy equal to [itex]\Delta[/itex], the pair gap. Since [itex]\Delta[/itex] is typically about the same at the equilibrium deformation and at the fission barrier, you typically won't get any huge difference in fission probabilities for this reason.

    The article says:
    What I get from this is:
    (1) The effect is hard to calculate, so presumably it can't just be explained by some generic argument based on the ordinary Strutinsky-style calculations, which are easy to calculate.
    (2) The effect has something to do with the angular momentum of the unpaired nucleons.

    My guess from the article would be that it's something like the following. The odd nucleus has some angular momentum K in its ground state, which is determined by the [itex]\Omega[/itex] quantum number of odd nucleon (since the ground state is, I believe, prolate in these nuclei). The state of lowest potential energy at the fission barrier has some other angular momentum, which is different. Since K is an approximately conserved quantum number, the nucleus is probably forced to tunnel out through a barrier that is effectively higher. The effect might be hard to calculate since (1) we don't know the single-particle energy levels at high deformation with good precision, and (2) it's hard to tell how good a conserved quantum number K is.

    But this is just my guess. I could be totally wrong.
     
  18. Apr 11, 2010 #17

    Affirmative.
     
  19. Apr 12, 2010 #18
    If an island of stability is created that lasts days, weeks, years, or longer then those can be used to create even more massive elements in experiments.
     
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