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Heavy elements

  1. Jan 25, 2016 #1


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    Today's APOD http://apod.nasa.gov/apod/ap160125.html
    Shows this fascinating table. What a pity that is doesn't show isotopes.

    Strange are Ba, La, Ce which are shown as large star but not supernova.

    The article says that the origin of Cu is not well known. Fascinating.

    I'm curious about the large star elements heavier than iron. Is neutron capture the only mechanism for their formations?

    I'm also curious about transport. How did "large star" elements, not supernova, get transported to the sun's primordial dust cloud? Zinc for example. We have lots of zinc.
    Last edited: Jan 25, 2016
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  3. Jan 25, 2016 #2


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    Perhaps I can guess at the answer to my own question. Most Zn in the universe is still trapped in the cores of the large stars where it was formed. A small fraction of the Zn was expelled in supernovas and transported here. Therefore Zn should be shown in the table as both large star and supernova. Correct?
  4. Jan 25, 2016 #3


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    Supernovae will certainly produce some of them, but it looks like most nuclei continue to capture more neutrons to get heavier elements.
    It is the dominant one, you always have some side-reactions.
    I think the table is really about the production process, so Zn produced in fusion where a supernova happened later would count as "large star". Supernovae help to emit large quantities of heavier elements into the surrounding medium, sure. Stellar winds contribute a bit as well.
  5. Jan 25, 2016 #4


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    Li was produced during the big bang.
  6. Jan 27, 2016 #5
    That was my first thought as well.
  7. Jan 27, 2016 #6


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    And through cosmic ray spallation. I'd have coloured that box half-BBN & half cosmic rays.

    The other head scratcher for me is arsenic. My understanding is that like Cu, the origin of As is somewhat unclear, but thought to be more likely r process than s. (see e.g. http://arxiv.org/pdf/1207.0518.pdf )
  8. Feb 4, 2016 #7


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    Heavy elements are produced by neutronification of lighter elements. There are any number of mechanisms by which this can occur, most of which are believed to occur as a product of stellar fusion. But even more energetic processes also occur in the cosmos that can contribute to this process.
  9. Feb 4, 2016 #8


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    Stellar fusion produces elements up to iron. Heavier elements are produce in supernovae
  10. Feb 4, 2016 #9


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    That's an oversimplification. Some heavier elements, as can be seen in the graphic in the OP, are produced in the s-process (slow neutron capture) in AGB stars (the 'large stars' category, but actually AGB stars are low-intermediate mass (<10 Msolar) stars. The graphic has some issues).

    Further, the site of the r-process (rapid neutron capture) isn't definitively supernovae. It has been difficult to reconcile models of supernovae with observed r-process abundances. Rather, the r-process may be located in neutron star mergers. Or, there may be several r-processes, and so several sites.
  11. Feb 5, 2016 #10


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    Once U and Pu are present, then some of the atoms will undergo fission, which would produce trace levels of Cu, Zn, Ga, Ge, As, Se, . . . and their complementary atoms.

    Basically for Z = 92, fission produces Z1 and Z2 = 92- Z1, so a fission of U produces 2 Pd, or (Rh, Ag), (Ru, Cd), (Tc, In), . . . (Zr, Te - very common for thermal neutron fission), . . . (As, Pr), (Ge, Nd), (Ga, Pm), . . .

    For fission of Pu, As is produced with Sm. As-75 however is produced in about 1E-11 fissions, so it more likely come from neutron capture by Ge-74, and subsequent β- decay of Ge-75.

    Then any of the fission products are subject to neutron capture and neutron spallation, or cosmic ray spallation.

    Select a location on the chart and zoom 1 to look at particular nuclides.

    Transuranic elements were identified in the residues (fallout) of nuclear weapons tests.
    "Production of Very Heavy Elements in Thermonuclear Explosions-Test Barbel"
    http://journals.aps.org/prl/abstract/10.1103/PhysRevLett.14.962 (purchase necessary)

    "Einsteinium was first identified in December 1952 by Albert Ghiorso and co-workers at the University of California, Berkeley in collaboration with the Argonne and Los Alamos National Laboratories, in the fallout from the Ivy Mike nuclear test."

    "Fermium was first discovered in the fallout from the 'Ivy Mike' nuclear test (1 November 1952), the first successful test of a hydrogen bomb."
    Last edited: Feb 5, 2016
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