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The nuclear underpinnings of Cosmogenic Nuclides. David Argento. Outline. Atomic and particle basics Atomic structure Major groups of subatomic particles Nuclear forces, structures and processes Four primary forces Radioactivity Forms of radiation. Before we launch. David Argento - PowerPoint PPT Presentation
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David Argento
The nuclear underpinnings of Cosmogenic Nuclides
David Argento
David Argento
Outline
• Atomic and particle basics– Atomic structure– Major groups of subatomic particles
• Nuclear forces, structures and processes– Four primary forces– Radioactivity– Forms of radiation
David Argento
Before we launch
• David Argento– Graduate student– JHN423– dargento@u.washington.edu
• References– Hyperphysics: http://hyperphysics.phy-astr.gsu.edu/hbase/HFrame.html– Wickipedia: useful, but be very skeptical– Hundreds of papers
• Apologies for errors, omissions, over simplicity, over complication, and pace.
David Argento
The Atom
electronelectron
proton
neutron
David Argento
Quarks
David Argento
Subatomic Particle Families & Generations
David Argento
Back to the nucleus
• What happens with similar charged objects?
10-15m10-10m
FE = ~100N
FG = ~10-35N
221
r
QkQFE
David Argento
Forces
Force Range Primary source/ interaction
Gravity Infinite Mass
Electromagnetic Infinite charge
Weak nuclear ~10-18m W and Z bosons, neutrinos and quarks
Strong Nuclear ~10-15m Gluons and nucleons
David Argento
Nuclear Stability
• The nucleus is stable in specific proton and neutron combinations
• Stability is based on electric-nuclear force balance
• Unstable nuclei will decay to achieve stability• Eject energy, electrical charge and nucleons
(protons and neutrons)• Thus…
David Argento
Radioactivity
• Gamma radiation– Electromagnetic
radiation
• Alpha radiation– Helium nucleus
• Beta radiation– Electron or positron
• Neutrons
• Neutrinos
• Fission
David Argento
Gamma Radiation
• Electromagnetic Radiation
David Argento
Alpha radiation
• Energetic ejection of helium-4 in 2+ state (no electrons)
David Argento
Beta Radiation
• Energetic ejection of electron or positron
David Argento
Neutrons
• Ejection of neutrons (low to high energy)
• Can also accompany other decay modes
David Argento
Neutrinos
• Weakly interacting, extremely small mass, and accompanies most, radioactive decay
• Not important for this the purpose of this class, but there is promise for use as probe of the interior of the earth (McDonough, W. F., Mapping the interior of the Earth, Science, 31, August 2007, pp1177 - 1178)
David Argento
Fission
• Not important for this class, but an important aspect of radioactive decay
• In-situ neutron source, must be corrected for if fissile material is present
David Argento
Probability and the Half life
• Each and every atom of an isotopic species has the same probability of decaying during a period of time.
• This results in a set fraction of the population decaying in the same time period, regardless of total population
• Each isotope is different
David Argento
Decay Curve
David Argento
Modeling exponential decay
2/1
2
10
T
t
NN
toeNN
David Argento
Population change
• Take the derivative:
Ndt
dN
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