Beta Decay

There are two types of beta decay: beta-minus and beta-plus

Beta-Minus Decay

In beta-minus decay, a neutron in an unstable nucleus transforms into a proton. As a result of this transformation, the nucleus emits an electron, known as a beta-minus particle, and an antineutrino, a nearly massless particle with no charge. The electron has a mass that is (1/1836)th of a proton’s mass, (1/1838)th of a neutron’s mass, and a charge of -1. This process increases the atomic number of the element by one, effectively changing it into a different element.

The nuclear equation representing a beta-minus decay is:

\[ ^{A}_{Z}X \rightarrow \text{ }^{A}_{Z+1}Y + e^{-} + \bar{\nu} \]

Where:

– A is the mass number

– Z is the atomic number

– \(^{A}_{Z}X\) is the parent nucleus

– \(^{A}_{Z+1}Y\)  is the daughter nucleus

– \(e^{-}\) is the emitted electron

– \( \bar{\nu} \) is a antineutrino

Examples

1. Carbon-14 to Nitrogen-14

The atomic number increases from 6 to 7, changing the element from carbon to nitrogen.

2. Tritium (Hydrogen-3) to Helium-3

The atomic number increases from 1 to 2, transforming from an isotope of hydrogen to an isotope of helium.

3. Potassium-40 to Calcium-40

Beta-Plus Decay or Positron Emission

In beta-plus decay, a proton in the nucleus is converted into a neutron. The nucleus emits a positron, known as a beta-plus particle, and a neutrino. A positron is the antimatter counterpart of an electron, having the same mass but a positive charge (+1). Beta-plus decay decreases the atomic number by one, resulting in the formation of a different element.

The chemical equation representing a beta minus decay is:

Where:

– \(^{A}_{Z}X\) is the parent nucleus

– \(^{A}_{Z-1}Y\)  is the daughter nucleus

– \(e^{+}\) is the emitted positron

– \( \nu \) is a neutrino

Examples

1. Fluorine-18 to Oxygen-18

The atomic number decreases from 9 to 8, indicating that fluorine transforms into oxygen.

2. Magnesium-23 to Sodium-23

3. Nitrogen-13 to Carbon-13

Neutrinos, being massless and chargeless particles, are essential because they carry energy and momentum, allowing a balanced decay process. Although neutrinos interact very weakly with matter, making them difficult to detect, their existence is fundamental to our understanding of nuclear reactions and the weak nuclear force that governs beta decay.

Beta decay follows fundamental conservation laws, including the conservation of charge and energy. These laws ensure that the total charge and the total energy before and after the decay remain balanced.

The energy released during beta decay is shared between the beta particle and the neutrino. This results in a continuous energy spectrum for beta particles, as the energy is not fixed but varies depending on the distribution between the two emitted particles.

• Medical Imaging and Treatment: Beta-plus decay is the basis for Positron Emission Tomography (PET) scans, a crucial tool in medical diagnostics for detecting cancers and monitoring brain activity.
• Carbon Dating: Beta-minus decay of carbon-14 is used in radiocarbon dating to determine the age of archaeological and geological samples, such as fossils and artifacts.
• Nuclear Energy: Beta decay plays a role in the decay of fission products in nuclear reactors, contributing to the management of nuclear waste.
• Environmental Monitoring: Beta-emitting isotopes are used to track pollution and study the movement of contaminants in the environment.
• Material Testing: Beta particles are used in thickness gauges to measure the thickness of materials like paper, metal, and plastic in industrial processes.