Beta decay

Beta Decay Experiment for Schools, Teachers, and Students

Beta decay is a type of radioactive decay in which an unstable atomic nucleus transforms into a more stable state by emitting a beta particle (β), which can be either an electron (β⁻) or a positron (β⁺).

Types of Beta Decay

1. Beta Minus Decay (β⁻)

• A neutron in the nucleus is converted into a proton, emitting an electron (β⁻) and an antineutrino (ν̅ₑ).
• The atomic number (Z) increases by 1, but the mass number (A) remains unchanged.
• Reaction:
  A_Z X → A_{Z+1} Y + β⁻ + ν̅ₑ

2. Beta Plus Decay (β⁺)

• A proton in the nucleus is converted into a neutron, emitting a positron (β⁺) and a neutrino (νₑ).
• The atomic number (Z) decreases by 1, but the mass number (A) remains unchanged.
• Reaction:
  A_Z X → A_{Z-1} Y + β⁺ + νₑ

3. Electron Capture (EC)

• A proton in the nucleus captures an orbital electron, converting into a neutron and emitting a neutrino (νₑ).
• The atomic number (Z) decreases by 1, and the mass number (A) remains unchanged.
• Reaction:
  A_Z X + e⁻ → A_{Z-1} Y + νₑ

Examples

1. Beta Minus Decay of Carbon-14

¹⁴₆C → ¹⁴₇N + β⁻ + ν̅ₑ
Carbon-14 decays into nitrogen-14 by emitting an electron and an antineutrino.

2. Beta Plus Decay of Sodium-22

²²₁₁Na → ²²₁₀Ne + β⁺ + νₑ
Sodium-22 decays into neon-22 by emitting a positron and a neutrino.

3. Electron Capture in Potassium-40

⁴⁰₁₉K + e⁻ → ⁴⁰₁₈Ar + νₑ
Potassium-40 undergoes electron capture to form argon-40.

Energy Release

The energy released (Q) in beta decay is shared between the beta particle, neutrino (or antineutrino), and the recoiling daughter nucleus. The energy spectrum of beta particles is continuous due to this distribution.

Key Features of Beta Decay

• Beta decay involves the weak nuclear force.
• The emitted beta particles (β⁻ or β⁺) have high energy and medium penetration power.
• The process conserves charge, lepton number, and energy.
• A neutrino (νₑ) or antineutrino (ν̅ₑ) is always emitted to ensure momentum conservation.

Applications of Beta Decay

1. Carbon Dating

Beta decay of carbon-14 is used to determine the age of archaeological samples.

2. Medical Imaging

Positron emission in β⁺-decay is the basis of PET scans.

3. Nuclear Energy

Beta decay products contribute to the heat generated in nuclear reactors.

4. Scientific Research

Beta decay is studied to understand weak interactions in particle physics.

Observations

• Beta minus decay increases the atomic number, while beta plus decay decreases it.
• Electron capture occurs in proton-rich nuclei, where positron emission is energetically unfavorable.
• The emitted beta particles follow a continuous energy spectrum, indicating the involvement of neutrinos.

Beta decay is a fundamental nuclear process governed by the weak interaction. It plays a vital role in radioactive decay, nuclear stability, and numerous scientific and practical applications.