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1. Introduction to Radiochemistry NUSC 341-3
2. Forces in Matter and the Subatomic Particles Chapter 1
3. What is Nuclear Science? Nuclear science: study of structure, properties, and interactions of atomic nuclei at fundamental level.
nucleus contains almost all mass of ordinary matter in a tiny volume
understanding behavior of nuclear matter under normal conditions
and conditions far from normal a major challenge
extreme conditions existed in the early universe, exist now in the core
of stars, and can be created in the laboratory during collisions
between nuclei (TRIUMF)
Nuclear scientists investigate by measuring the properties, shapes, and decays of nuclei at rest and in collisions.
This course covers low energy, or low temperature, nuclear science
=> properties of the nucleus
4. Why should we bother?
5. Interactions Electromagnetic
e- (lepton) bound in the atoms by the electromagnetic force
Neutrino observed in beta decay.
Quarks are bound in together by the strong force
in nucleons. Nuclear forces bind nucleons into
Gravitational interaction between the elementary particles
is in practice very small compared to the other three.
7. Standard Model Attempts to explain all phenomena of particle physics in terms of properties and interactions of a small number of three distinct types.
Bosons: spin-1; force carriers
These are assumed to be elementary.
8. Standard Model
9. Hadrons Hadrons: any strongly interacting subatomic particle; composed of quarks.
There are 2 categories:
Baryons: fermions, make of 3 quarks
Mesons: bosons, made of quark, antiquark
Mesons are composite mesons, but they are not composed of mesons, because the quarks are spin-1/2 particles and therefore they are fermions.Mesons are composite mesons, but they are not composed of mesons, because the quarks are spin-1/2 particles and therefore they are fermions.
10. Antiparticles Electron (e-) Positron (e+)
Particles and antiparticles (such as the pair highlighted in pink) are created in pairs from the energy released by the collision of fast-moving particles with atoms in a bubble chamber. Since particles and antiparticles have opposite electrical charges, they curl in opposite directions in the magnetic field applied to the chamber.
12. Building Blocks Molecules consists of atoms.
An atom consists of a nucleus, which carries almost all the mass of the atom and a positive charge Ze, surrounded by a cloud of Z electrons.
Nuclei consist of two types of fermions: protons and neutrons, called also nucleons.
Nucleons consists of three quarks.
16. Mass Nuclear and atomic masses often given in
u: atomic mass unit
12.000 u = 12 daltons mass of a neutral 12C atom
1 u = 1.6605 x 10-27 kg
Mass and energy are interchangeable
E = mc2
where energy usually expressed in MeV
1 MeV = 1.602 x 10-13 J
1 u = 931.5 MeV/c2
18. Classification of Nuclides Stable nuclei: 264; 16O
Primary natural radionuclides: 26; very long half-lives; 238U with t1/2 = 4.47 x 109 y
Secondary natural radionuclides: 38; 226Ra t1/2 = 1600 y decay of 238U
Induced natural radionuclides: 10; cosmic rays; 3H t1/2 = 12.3 y; 14N(n,t)12C
Artificial radionuclides: 2-4000, 60Co, 137Cs
19. Periodic Table
20. Chart of Nuclei plot of nuclei as a function of Z and N
Not just one box per element
21. Chart of Nuclides
22. or Segre Chart plot allows various nuclear properties to be understood at a glance, similar
to how chemical properties are understood from the periodic chart
~ 2500 different nuclei known
theorists guess at least 4000 more to be discovered at higher neutron numbers, higher mass
proton-rich side (left of stable): proton dripline cannot add another proton, it drips off dripline is known/accessible to experiments
neutron-rich side (right of stable): neutron dripline cannot add another neutron, it drips off dripline is unknown neutron-rich nuclei difficult to produce/study
mass (above stable) cannot add another proton or neutron limit unknown again, difficult to produce/study
island of stability predicted near Z = 114; not yet observed
24. Thorium Decay Chain (4n + 0)
26. The Actinium Decay Series (4n +3) 235U ? ? 207Pb (7 alphas and 4 betas)
7.04 x 108 y
27. An Extinct Natural Decay Chain Neptunium decay series (4n + 1)
237Np (t1/2 = 2.14 x 109 y ) ??209Bi
28. End of Chapter 1 Any questions?