218Po

…formation of ‘exotic’ radioactive nuclei (in nature)…new elements created e.g., Pa, Ac, Ra, Rn, PooPoo

‘218Po =Radium A’

‘218At =Radium B’

C

D

E

210Po=Radium ‘F’ Radon

=‘Emanation’

‘Radium’

C’

C’’

The Natural Decay Chain for 238U

Aside: information here is used extensively in environmental monitoring; + radioactive dating – age of the earth ~109 yrs…evidence for evolution....

‘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.

Most energetically stable nuclei in the middle, More exotic, unstable nuclei at the edges….

How Far Can We Go ?

• What are the ‘nuclear limits’ ?

• 2 proton radioactivity

• What is the heaviest element ?

• How are the heavier elements formed ?

Physics aims and regions for the Stopped RISING Campaigns (2006-8)

Accelerator facility at GSI-Darmstadt

Beam Currents: 238U - 108 ppssome medium mass nuclei- 109

pps (A~130)

Ion-by-ion identification with the FRS

TOF

E

Cocktail of secondary, exotic fragments with ~ x00 MeV/u thru. FRS.

Separate and identify event-by-event. Chemically independent.

What about ‘inside’ the nucleus(i.e. nuclear ‘structure’) ?

• Can we see ‘inside’ the nucleus ?

• What does it tell us?

Nuclear Excited States – Nuclear Spectroscopy.Nuclei can exist in either the ground state or an excited stateEach nucleus is different….but groups of structural patterns do appear….

• Nuclear states labelled by spin and parity quantum numbers and energy. • Excited states (usually) decay by gamma rays (non-visible, high energy light).• Measuring gamma rays gives the energy differences between quantum states.

gamma ray decay

Euroball IV at Strasbourg

New forms of radioactivity at the proton drip line– 2 proton decay

Blank, Pfutzner et al.,

For a ‘typical’ nucleus,

Nuclear Volume A (= number of protons and neutrons)

Since for a sphere, V = 4R3/3

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)

The probability of a beam of ‘neutron-rich’ lithium-11 isotopes colliding on carbon target was much larger than expected.

Lithium beam

targetdetector

Nuclear ‘halos’ and Borromean Nuclei….Nuclear ‘halos’ and Borromean Nuclei…. Nuclear ‘halos’ and Borromean Nuclei….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 oneand the other two fall apart….

4n4n

BorromeanHalo states

tetraneutron

Protondripline

(SOME) BiG NUCLEAR PHYSICS’ QUESTIONS TO BE ADDRESSED

• Does the ordering of nuclear quantum states change ?•How robust are the magic numbers?•What are the limits of nuclear existence?

K-electrons

L-electrons

T1/2 = 10.4 s205Au126

202Pt

Nuclear Excited States – Nuclear Spectroscopy (recall).

• Nuclear states labelled by spin and parity quantum numbers and energy. • Excited states (usually) decay by gamma rays (non-visible, high energy light).• Measuring gamma rays gives the energy differences between quantum states.

gamma ray decay

Evidence for nuclear shell structure…..energy of 1st excited state in even-even nuclei….E(2+).

What do we expect ?

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

(SOME) BiG NUCLEAR PHYSICS’ QUESTIONS TO BE ADDRESSED

• Does the ordering of nuclear quantum states change ?•How robust are the magic numbers?•What are the limits of nuclear existence?

K-electrons

L-electrons

T1/2 = 10.4 s205Au126

202Pt

N=82N=126

• A (big!) problem, can’t reproduce the observed elemental abundances.

• We can ‘fix’ the result by changing the shell structure (i.e. changing

the magic numbers)….but is this scientifically valid ? N=126N=82

• Need to look at N=82 and 126 ‘exotic’ nuclei in detail….

Turning Lead into Gold and Platinum….

Rotations in the UniverseR

evo

luti

on

s/se

c

Typical size (cm)

The 12 valence particles The 12 valence particles move in equatorial move in equatorial orbits, driving the orbits, driving the nucleus to an oblate nucleus to an oblate shape!shape!

158Er at ‘High Spins’ from Daresbury Lab

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….

• 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.

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.

(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.

(‘Big’) Physics Questions from the STFC Nuclear Physics Advisory Panel

What is the Nature of Nuclear Matter?• What are the limits of nuclear existence?• How do simple patterns emerge in complex nuclei?• Can nuclei be described in terms of our understanding of the

underlying fundamental interactions?• What is the equation-of-state of nuclear matter?• How does the ordering of quantum states change in extremely

unstable nuclei?• Are there new forms of structure and symmetry at the limits of

nuclear existence? What are the Origins of the Elements?• How, and where, were the heavy elements synthesised?• What are the key reaction processes that drive explosive

astrophysical events such as supernovae, and X-ray bursts?• What is the equation-of-state of compact matter in neutron stars?• What are the nuclear processes, and main astrophysical sites, that

produce the γ-ray emitting radionuclides observed in our galaxy?• How do nuclear reactions influence the evolution of massive stars,

and how do they contribute to observed elemental abundances?