Prof. Paddy Regan Department of Physics

Nuclear Spectroscopy: From Natural Radioactivity to Studies of the Most Exotic Isotopes.

• Prof. Paddy Regan

• Department of Physics

• University of Surrey, Guildford,

• &

• Radioactivity Group,

• National Physical Laboratory,

• Teddington

• [e-mail]

Outline of talk

• Elements, Isotopes and Isotones

• Alpha, beta and gamma decay

• Primordial radionuclides…..why so long ?

• Internal structures, gamma rays and shells.

• How big is the nuclear chart ?

• What could this tell us about nucleosynthesis?

Some current nuclear physics questions

• 286 combinations of protons and neutrons are either stable or have decay half-lives of more than 500 million years.

• What are the limits of nuclear existence…i.e. how many different nuclear species can exist?

• N/Z ratio changes for stable nuclei from ~1:1 for light nuclei (e.g., 16O, 40Ca) to ~1.5 for 208Pb (126/82 ~ 1.5)

• How does nuclear structure change when the N/Z ratio differs from stable nuclear matter?

Accelerator facility at GSI-Darmstadt

An Efficient Way to Make Exotic Nuclei: Projectile Fragmentation Reaction Process

A few physics examples….

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

Summary

• Radionuclides (e.g. 235U, 238U, 232Th, 40K) are everywhere.

• Radioactive decays arise from energy conservation and other (quantum) conservation laws.

• Characteristic gamma ray energies tell us structural info.

• The limits for proton-richness in nuclei has been reached.

• Neutron-rich nuclei are harder to make at the extremes, but we are starting to be able to reach r-process radionuclides.

• Does the nuclear shell model remain valid for nuclei with ‘diffuse neutron skins’ ?

• FAIR will increase dramatically our reach of nuclear species for experimental study