Radioactivity Flashcards
Typical Nuclear sizes
1fm
Radioactive Decay
definition
Spontaneous emission of radiation that changes state of the nucleus
What is alpha Decay
The helium nucleus is emitted from the parent nucleus.
Strongly ionising, heavy, charge of 2e. Damaging in the body
What is Beta Decay
High energy electron or positron is emitted from nucleus.
Less ioinsing than alpha but faster and lower charge
Beta plus deacy
proton -> neuton + neutrino + positron
Beta minus decay
neutron -> proton + antineutrino + electron
What is Gamma Decay?
nucleus de-excites and emits gamma ray photons. Very energetic, weakly ionoising and uncharged
Activity definition
Number of decays per second
Mean lifetime in radioactive decay
equation
τ =
integral (t|dN/dt|) dt
/
integral (|dN/dt| )dt
.
Activity at which decay occurs equation
A = λN
What decay processes unstable nucleus
Alpha and Beta decay
What decay changes nuclear species
gamma decay
Energy Release equation
Q =
[(Sum of nuclear masses of reactants) −
(Sum of nuclear masses of products)]c^2
What is required for a decay to be energetically possible?
Q>0
What decay is more significant for heavier nuclei and what is it caused by
Alpha emission - Coulomb Repulsion effect
As Coulomb effect increases with Z^2 and nuclear binding force increases with A
Nuclear Mass conversion equation
Nuclear mass = Atomic MASS - Z(Mass of electrons)
What is the Geiger Nuttall Rule
Relates energies of emitted alpha particle and half-lives of nuclides.
- Alpha particle is pre-formed in nucleus
- Alpha particle moves in spherical pot well created by daughter nucleus.
- Alpha particle has energy equal to Q as most energy release is carried by particle
What are the three regions of interest in the Geiger Nuttall Rule?
where r represents the distance between the α particle and daughter
nucleus.
1 - r<a; potential well has depth of -v0. Particle is classically confined.
2 - outside r<a repulsive coulomb potential present w cut off at r=a. For a < r < b, there is a barrier region, where the potential energy is greater than
Q
3 - 3. The region r > b is classically permitted outside the barrier.
