beta decay
A Look at Nuclear Science and Technology Larry Foulke
Atomic and Nuclear Physics – The Einstein Connection 2.3 Seeking Stability
Nuclear Stability (Proton Rich) • Too many protons -or- nucleus too large
p p
n
p p
p
n
n p
p
p n p
– Long-range repulsive Coulomb forces overpower shortrange attractive nuclear forces.
Nuclear Force (Attractive)– Nucleus is unstable. Coulomb Force (Repulsive) 2
Nuclear Stability (Neutron Rich) • Too many neutrons p p
n
n n
n
n
n
n n
p n p
– Significant asymmetry between the number of protons and number of neutrons creates an imbalance in the internal energy levels of the two types of nucleons.
– Excess neutrons cause the nucleus to be at a higher than desired energy state.
– Nucleus is unstable.
3
Nuclear Stability p p
n p
p
p n
n
p n
p
• Too many protons – Unstable
p
p
p p
n n
n n
n n
p n
n
• Too many neutrons – Unstable
p
n
n p n
p n p
n
• 1< neutrons / protons 90 9
Nuclear Decay Modes
• Decay Mode 3: Change nucleon flavor – Most common type of decay for nuclei with Z < 90. – All processes that change nucleon flavor are referred to as beta decay. – Two basic modes of beta decay • Negative – Turns a neutron into a proton – Beta-Negative decay, double Beta-Negative Decay • Positive – Turns a proton into a neutron – Positron emission, electron capture, double positron emission, double electron capture 10
Negative Beta Decay • Beta Decay (Negative) – Affects unstable nuclei with more neutrons than protons. – Nuclei changes neutron to proton and emits a beta particle and an antineutrino. Beta particles Mass
Atomic and Nuclear Physics – The Einstein Connection 2.3 Seeking Stability
Nuclear Stability (Proton Rich) • Too many protons -or- nucleus too large
p p
n
p p
p
n
n p
p
p n p
– Long-range repulsive Coulomb forces overpower shortrange attractive nuclear forces.
Nuclear Force (Attractive)– Nucleus is unstable. Coulomb Force (Repulsive) 2
Nuclear Stability (Neutron Rich) • Too many neutrons p p
n
n n
n
n
n
n n
p n p
– Significant asymmetry between the number of protons and number of neutrons creates an imbalance in the internal energy levels of the two types of nucleons.
– Excess neutrons cause the nucleus to be at a higher than desired energy state.
– Nucleus is unstable.
3
Nuclear Stability p p
n p
p
p n
n
p n
p
• Too many protons – Unstable
p
p
p p
n n
n n
n n
p n
n
• Too many neutrons – Unstable
p
n
n p n
p n p
n
• 1< neutrons / protons 90 9
Nuclear Decay Modes
• Decay Mode 3: Change nucleon flavor – Most common type of decay for nuclei with Z < 90. – All processes that change nucleon flavor are referred to as beta decay. – Two basic modes of beta decay • Negative – Turns a neutron into a proton – Beta-Negative decay, double Beta-Negative Decay • Positive – Turns a proton into a neutron – Positron emission, electron capture, double positron emission, double electron capture 10
Negative Beta Decay • Beta Decay (Negative) – Affects unstable nuclei with more neutrons than protons. – Nuclei changes neutron to proton and emits a beta particle and an antineutrino. Beta particles Mass
