13.14. Atomic nucleus, isotopes, radiation Flashcards
What is an isotope?
same atomic number, different atomic mass number (same number of protons and electrons but different neutrons)
What is the N/Z ratio?
neutron / proton ratio : generally increases with increasing atomic number
What is beta decay?
occurs during transformation of a particle contained in the atomic nucleus and emission of multiple particles
What is beta minus decay?
surplus of neutrons, turns into 1 positron and emits 1 electron and an antineutrino
What is gamma decay?
unstable atomic nuclei dissipates excess energy bu spontaneous electromagnetic process : releases high E photon after alpha or beta radiation
What is the energy range of gamma decay photons?
keV-MeV
What ate the 2 artificial ways to produce isotopes?
via accelerator (charged nuclei strike) or via reactors (neutron flux)
What is an isomeric transition?
When there is delay in the emission of gamma photon because there is a metastable state in the “daughter nucleus”
What is the minimal energy required for pair production and why?
1.022 MeV : 2x511kEV, because the photon must have more energy than the sum of the rest mass energies
What is the definition of activity?
the amount of decays in a unit time
What is the unit of activity?
Bequerel : 1 decay/s
What is the decay constant?
probability of the decay 1/s
Which particles can directly ionize matter?
particles with electric charge
Which particles cannot directly ionize matter?
uncharged particles (photons)
How does the alpha particle interact with matter?
directly ionize atoms of matter by coulomb’s force. Short effective range bc heavy : low penetration depth
How does the beta minus particle interact with matter?
small charged particle : directly ionizes atoms of matter by coulomb force. since smaller and less charge, it penetrates ore than alpha particles
How does the beta plus particle interact with matter?
undergoes annihilations
What is neutron radiation?
a form of ionization radiation that presents as free neutrons
How does neutron radiation happen?
- collision with nucleus
- nuclear fission / fusion : release of neutrons
- may lead to propagation (triggers more neutron radiation)
Why can proton radiation be precisely radiated?
because its radiation dose peaks and then decreases completely instead of X-rays where it decreases progressively
What is the Bragg curve?
plots the energy loss of radiation during its travel through matter. Radiation dose vs penetration depth
What is the Bragg peak?
where the maximum dose is achieved
