Alpha, Beta & Gamma Decay [Complete Discussion]

Introduction to Radioactive Decay

In this section, the speaker introduces radioactive decay and its three types: alpha decay, beta decay, and gamma decay.

Types of Radioactive Decay

• Alpha decay involves emission of alpha particles which have low penetrative power.

• Beta decay involves emission of beta particles which can penetrate through few centimeters in aluminum.

• Gamma photons have the highest penetrative power and can penetrate through few centimeters in lead. They are uncharged in nature.

Alpha Decay Process

In this section, the speaker explains what an alpha particle is and how it is emitted during an alpha decay process.

What is Alpha Decay?

• Alpha particles consist of two protons and two neutrons, making them a helium nuclei with four nucleon particles.

• A nucleus usually emits an alpha particle when it becomes unstable due to its size being greater than 210.

Why Does Alpha Decay Occur?

• The nucleus is held together by the nuclear force but there is also coulombic repulsion between proton pairs that tries to break apart the nucleus.

• The nuclear force is much stronger than coulombic repulsion at short distances (around 1 femtometer to 3 femtometers).

• When a nucleus is small or mid-range in size, the nuclear force can hold it together effectively. However, for larger nuclei, the coulombic repulsion becomes too strong and causes instability leading to alpha decay.

Beta Decay Process

In this section, the speaker explains what a beta particle is and how it is emitted during a beta decay process.

What is Beta Decay?

• Beta particles are high-energy electrons or positrons that are emitted from the nucleus during beta decay.

• Beta decay occurs when there is an imbalance between the number of neutrons and protons in the nucleus.

Types of Beta Decay

• There are two types of beta decay: beta-minus (β-) and beta-plus (β+) decay.

• In β- decay, a neutron in the nucleus decays into a proton, an electron, and an antineutrino. The electron is then emitted from the nucleus as a beta particle.

• In β+ decay, a proton in the nucleus decays into a neutron, a positron, and a neutrino. The positron is then emitted from the nucleus as a beta particle.

Gamma Decay Process

In this section, the speaker explains what gamma radiation is and how it is emitted during gamma decay.

What is Gamma Radiation?

• Gamma radiation consists of high-energy photons that are emitted from the nucleus during gamma decay. They have no mass or charge but have high penetrative power.

Why Does Gamma Decay Occur?

• Gamma rays are usually emitted after alpha or beta decay to release excess energy from the daughter nuclei that was not released during alpha or beta emission.

• During gamma emission, there is no change in atomic number or mass number of the daughter nuclei.

Nuclear Forces and Coulombic Repulsion

In this section, the speaker explains how nuclear forces and coulombic repulsion interact with each other in a nucleus.

Coulombic Repulsion

• Coulombic repulsion can exist between two nearest neighboring protons as well as between two protons on the extreme ends of a nucleus because it has a range of infinity.

• As the number of protons increases, the coulombic repulsion becomes larger and larger.

Nuclear Forces

• Nuclear forces are dominant only in ranges of distances from around 1 femtometer to 3 femtometers.

• A nucleon is attracted via nuclear force only with its nearest neighboring nucleons.

• The nuclear force exists locally gluing all the nucleons together with its nearest neighboring nucleons.

Size Limit

• When the size of the nucleus becomes too large, local nuclear forces which hold the nearest neighboring nucleons together become unable to dominate over coulombic repulsion which now becomes larger and larger because of increasing number of protons.

• A particular size limit is reached beyond which if the size of the nucleus grows then coulombic repulsion automatically dominates over nuclear force and tries to break apart the nucleus.

Alpha Decay

In this section, we learn about alpha decay process.

Unstable Nucleus

• Whenever a large unstable nucleus wants to become stable, it automatically tends to decrease its size by releasing some of the excess neutrons and protons which comes off in the form of alpha decay.

• Alpha decay helps a large size nucleus which is unstable to become stable by decreasing its size by releasing an alpha particle in this process.

Quantum Tunneling

• The nuclear potential has a barrier height of around 2.5 times greater than the kind of energy of the alpha particle. It is not possible classically for an alpha particle to come out of a nuclear potential which has a height greater than its energy. This is only possible because of quantum tunneling.

• Particles have a certain probability of penetrating through a potential barrier having a height greater than its kind of energy due to their wave mechanical behavior.

Gamma's Theory

• In Gamma's theory, the alpha particle exists independently inside the nuclear walls within the nuclear potential well and constantly collides with the nuclear wall, having a certain probability of penetrating through it every time it collides with it.

Radioactivity and Beta Decay

In this section, the speaker discusses radioactivity and beta decay. He explains that radioactivity is a probabilistic phenomenon and that beta decay can happen for small, medium, or large nuclei depending on the number of protons and neutrons.

Radioactivity

• Radioactivity is a probabilistic phenomenon.

• It comes as a result of quantum tunneling which is inherently probabilistic in nature.

Beta Decay

• Beta decay can happen for small, medium, or large nuclei depending on the number of protons and neutrons.

• The NZ graph shows the kinds of nuclear configurations that exist in nature. The stability curve represents those nuclear configurations in which the number of neutrons and number of protons leads to the most stable nuclear configurations.

• Nuclei with an excess number of protons or an excess number of neutrons are unstable. The only way they can become stable is when the excess number of protons will become a neutron or the excess number of neutrons will become a proton.

• Beta decay reactions involve transformations where a neutron becomes a proton or vice versa.

• Nuclear energy levels exist inside the nucleus just like electron energy levels exist around atoms. Neutrons and protons arrange themselves into ground state configuration where all necessary energy levels are occupied.

Overall, this section provides an introduction to radioactivity and beta decay. It explains how these phenomena work at a fundamental level by discussing nuclear energy levels, neutron-proton ratios, and stability curves.

Beta Decay Processes

This section explains the process of beta decay and how it occurs when there is an excess number of neutrons or protons in a nucleus. It also discusses the role of neutrinos in beta decay.

Conversion of Neutrons to Protons

• When there is an excess number of neutrons or protons, beta decay processes occur.

• The conversion of neutrons to protons leads to a more stable configuration with lower energy levels.

• Excess neutrons can be converted to a proton, while excess protons can be converted to a neutron.

• These transformations are known as beta decay processes.

NZ Graph and Stability

• Most nuclear configurations tend towards stability, which corresponds to almost equal numbers of neutrons and protons.

• As the size of the nucleus increases, more neutrons are required to balance Coulombic repulsion from increasing numbers of protons.

• The NZ graph shows that for increasing mass numbers, the number of neutrons exceeds that of protons.

Neutrinos in Beta Decay

• Beta particles emitted in beta decay reactions do not always have uniform kinetic energy and recoil direction compared to their parent nuclei.

• A neutrino is involved in this kind of beta decay reaction and takes away excess energy and momentum from the electron particle emitted during beta decay.

• Electron neutrinos are the matter version of neutrinos, while anti-neutrinos are the antimatter version.

Conclusion

This section concludes the video and mentions that a separate video will be made to discuss the history and hypothesis behind neutrinos.

• The video concludes by mentioning that a separate video will be made to discuss the history and hypothesis behind neutrinos.

Beta Decay and Gamma Decay

This section explains the two types of beta decay reactions, positron emission and electron capture. It also discusses gamma decay and other processes associated with nuclear energy level transitions.

Beta Decay Reactions

• Positive beta decay reactions occur when a nucleus has an excess number of protons that get converted to a new nucleus where the number of protons will be less.

• In positron emission, a proton gets converted to a neutron while emitting a positron and neutrino. In electron capture, a nearby electron from its nearest orbit is absorbed by the nucleus which leads to the conversion of proton into neutron and emission of neutrino.

• Inverse beta decay processes involve neutrinos being absorbed instead of emitted.

Gamma Decay

• Gamma decay occurs when nucleons transition from higher energy levels to lower energy levels leading to the emission of photons.

• The differences in energy during nuclear transitions are quite energetic, leading to the emission of gamma particles which are quite energetic.

• Internal conversions happen when an electron in the nearest neighboring orbit absorbs the energy from nucleon transition while internal pair creation happens when excess amount of energy leads to creation of an electron and positron pair.

Creation of a Positron and an Electron

In this section, the speaker explains the process of internal pair creation.

Internal Pair Creation

• Internal pair creation occurs when the energy is greater than the rest mass energy of an electron and a positron pair.

• This process involves the creation of a positron and an electron.