Positive and Negative Beta Emission

Beta Emission: Positive and Negative

Beta decay is a type of radioactive decay in which a nucleus emits a beta particle, transforming into a different element while conserving mass number but changing atomic number. There are two main types: beta-minus (β⁻) emission and beta-plus (β⁺) emission.

These processes help unstable nuclei achieve greater stability by adjusting the neutron-to-proton ratio.

Beta-Minus (β⁻) Emission

In beta-minus decay, a neutron in the nucleus is converted into a proton, emitting an electron (β⁻ particle) and an electron antineutrino (ν̄ₑ).

n → p + e⁻ + ν̄ₑ

The nuclear reaction for a parent nucleus ^A_ZX is:

^A_ZX → ^A_Z+1Y + e⁻ + ν̄ₑ

This occurs in neutron-rich nuclei (below the stability curve). Example: Carbon-14 decay.

Beta-Plus (β⁺) Emission

In beta-plus decay, a proton is converted into a neutron, emitting a positron (β⁺ particle) and an electron neutrino (νₑ).

p → n + e⁺ + νₑ

The nuclear reaction is:

^A_ZX → ^A_Z-1Y + e⁺ + νₑ

This occurs in proton-rich nuclei (above the stability curve). Example: Fluorine-18 used in PET scans.

Key Features of Beta Decay

The emitted beta particles have a continuous energy spectrum up to a maximum value, due to energy sharing with the (anti)neutrino. This was a puzzle until the neutrino's existence was proposed.

Beta decay adjusts the neutron-proton ratio toward the valley of stability on the nuclear chart.

Read also Electron Capture

Both types of beta emission are governed by the weak nuclear force and play crucial roles in astrophysics, medicine (e.g., radiotherapy, imaging), and dating techniques.

In beta-minus decay, what particle is emitted along with the electron?

A. Neutrino
B. Antineutrino
C. Proton
D. Positron

Why does the beta particle energy spectrum appear continuous?

A. Due to recoil of the nucleus
B. Energy sharing with the (anti)neutrino
C. Multiple decay paths
D. Detector resolution