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218 Po

218 Po. The Natural Decay Chain for 238 U. ‘Radium’. ‘ 218 At =Radium B’. 210 Po =Radium ‘F’. Radon =‘Emanation’. C’. ‘ 218 Po =Radium A’. E. C. D. C’’. Aside: information here is used extensively in environmental monitoring;

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218 Po

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  1. 218Po

  2. The Natural Decay Chain for 238U ‘Radium’ ‘218At =Radium B’ 210Po =Radium ‘F’ Radon =‘Emanation’ C’ ‘218Po =Radium A’ E C D C’’ Aside: information here is used extensively in environmental monitoring; + radioactive dating – age of the earth ~109 yrs…evidence for evolution....

  3. Most energetically stable nuclei in the middle, More exotic, unstable nuclei at the edges…. ‘Nuclei = combinations of protons (Z) and neutrons (N). Chart of the Nuclides = a ‘2-D’ periodic table…… <300 of the (Z,N) combinations are stable and make up’everyday’ atoms. ~7,000 other combinations are unstable nuclei.

  4. For a ‘typical’ nucleus, Nuclear Volume A (= number of protons and neutrons) Since for a sphere, V = 4R3/3 Thus nuclear radius, R A1/3  R= (1.2 x10-15m) A1/3 Rutherford Scattering experiments showed this relation to hold for all nuclei studied….so what’s new to learn…. Then… 1985 – the strange case of ‘Lithium -11’ (note stable lithium isotopes are Lithium-6 and Lithium-7)

  5. Lithium beam detector target The probability of a beam of ‘neutron-rich’ lithium-11 isotopes colliding on carbon target was much larger than expected…(remind you of anything?)…

  6. Nuclear ‘halos’ and Borromean Nuclei…. J.S. Al-Khalili & J.A. Tostevin, Phys. Rev. Lett. 76 (1996) 3903 Halo nuclei are examples of ‘Borromean’ systems, only bound with three Interactions…remove any one and the other two fall apart….

  7. Proton dripline Borromean Halo states 4n tetraneutron

  8. What about ‘inside’ the nucleus(i.e. nuclear ‘structure’) ? • Can we see ‘inside’ the nucleus ? • What does it tell us?

  9. Euroball IV at Strasbourg

  10. 158Er at ‘High Spins’ from Daresbury Lab The 12 valence particles move in equatorial orbits, driving the nucleus to an oblate shape!

  11. Rotations in the Universe Revolutions/sec Typical size (cm)

  12. How Far Can We Go ? • What is the heaviest element ? • What are the ‘nuclear limits’ ? • How are the heavier elements formed ?

  13. Super Heavy Elements? • Rutherford worked with decays from Thorium and Uranium the heaviest element (Z=90 & 92) known at the time. • He inferred their presence and other elements in their decay chains by characteristic alpha decay sequences….

  14. Elements Z=116 and 118 discovered from fusion of Calcium ions on radioactive targets of Californium and Curium (Oganessian et al., Phys. Rev. C74 (2006) 044602). • Periodic table has increased by 26 elements since Rutherford’s work on Uranium and Thorium decays.

  15. How are the heavy elements made ? Is it via the Rapid Neutron Capture (R-) Process ? T1/2 = 10.4 s 205Au126 K-electrons L-electrons 202Pt Many of the nuclei which lie on the r-process predicted path have yet to be studied. Do these radioactive nuclei act as we expect ?

  16. Evidence for nuclear shell structure…..energy of 1st excited state in even-even nuclei….E(2+). What do we expect ?

  17. large gaps in single-particle structure of nuclei…MAGIC NUMBERS = ENERGY GAPS

  18. N=82 N=126 We have a (big!) problem…can’t reproduce the observed elemental abundances... We can we ‘fiddle’ the result by reducing the shell effects (i.e. changing the magic numbers….) is this valid ? Need to look at N=126 ‘exotic’ nuclei in detail….

  19. Turning Lead into Gold and Platinum….

  20. Facility for Anti-Proton and Ion Research (FAIR) To be constructed at the current GSI site, near Darmstadt, Germany Will bring currently ‘theoretical nuclear species’ into experimental reach for the first time.

  21. (some) Nuclear Physics Research c. 2009. Nuclei comprise 99.9% of all matter we can see in the Universe and are the fuel that burns in stars. A comprehensive description of nuclei requires theoretical and experimental investigations of rare isotopes with unusual neutron-to-proton ratios. These nuclei are labeled exotic, or rare, because they are not typically found on Earth. They are difficult to produce because they usually have extremely short lifetimes. The goal of a comprehensive description and reliable modeling of all nuclei represents one of the great intellectual opportunities for physics in the twenty-first century.

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