ALPHA PARTICLES: DISCOVERY, CHARACTERISTICS, APPLICATIONS - PHYSICAL - 2024

The alpha particles (or α particles) are nuclei of helium atoms ionized therefore have lost electrons. Helium nuclei are made up of two protons and two neutrons. So these particles have a positive electric charge whose value is twice the charge of the electron, and their atomic mass is 4 atomic mass units.

Alpha particles are emitted spontaneously by certain radioactive substances. In the case of Earth, the main known natural source of alpha radiation emission is radon gas. Radon is a radioactive gas that is present in soil, water, air, and some rocks.

Discovery

It was throughout the years 1899 and 1900 when physicists Ernest Rutherford (who worked at McGill University in Montreal, Canada) and Paul Villard (who worked in Paris) differentiated three types of filings, named by Rutherford himself as: alpha, beta and gamma.

The distinction was made based on their ability to penetrate objects and their deflection by the effect of a magnetic field. By virtue of these properties, Rutherford defined alpha rays as having the lowest penetration capacity in ordinary objects.

Thus, Rutherford's work included measurements of the ratio of an alpha particle's mass relative to its charge. These measurements led him to hypothesize that the alpha particles were doubly charged helium ions.

Finally, in 1907 Ernest Rutherford and Thomas Royds succeeded in showing that the hypothesis established by Rutherford was true, thus showing that alpha particles were doubly ionized helium ions.

characteristics

Some of the main characteristics of alpha particles are as follows:

Atomic mass

4 atomic mass units; that is, 6.68 ∙ 10 ^-27 kg.

Load

Positive, twice the charge of the electron, or what is the same: 3.2 ∙ 10 ^-19 C.

Speed

Of the order of between 1.5 · 10 ⁷ m / s and 3 · 10 ⁷ m / s.

Ionization

They have a high capacity to ionize gases, transforming them into conductive gases.

Kinetic energy

Its kinetic energy is very high as a consequence of its great mass and speed.

Penetration capacity

They have a low penetration capacity. In the atmosphere they lose speed rapidly when interacting with different molecules as a consequence of their great mass and electrical charge.

Alpha decay

Alpha decay or alpha decay is a type of radioactive decay that consists of the emission of an alpha particle.

When this happens, the radioactive nucleus sees its mass number reduced by four units and its atomic number by two units.

In general, the process is as follows:

^A _Z X → ^A-4 _Z-2 Y + ⁴ ₂ He

Alpha decay normally occurs in the heavier nuclides. Theoretically, it can only occur in nuclei somewhat heavier than nickel, in which the overall binding energy per nucleon is no longer minimal.

The lightest known alpha-emitting nuclei are the lowest mass isotopes of tellurium. Thus, tellurium 106 (¹⁰⁶ Te) is the lightest isotope in which alpha decay occurs in nature. However, exceptionally ⁸ Be can be broken down into two alpha particles.

Since alpha particles are relatively heavy and positively charged, their mean free path is very short, so they quickly lose their kinetic energy at a short distance from the emitting source.

Alpha decay from uranium nuclei

A very common case of alpha decay occurs in uranium. Uranium is the heaviest chemical element found in nature.

In its natural form, uranium occurs in three isotopes: uranium-234 (0.01%), uranium-235 (0.71%), and uranium-238 (99.28%). The alpha decay process for the most abundant uranium isotope is as follows:

²³⁸ ₉₂ U → ²³⁴ ₉₀ Th + ⁴ ₂ He

Helium

All the helium that currently exists on Earth has its origin in the alpha decay processes of different radioactive elements.

For this reason, it is usually found in mineral deposits rich in uranium or thorium. Similarly, it is also associated with natural gas extraction wells.

Toxicity and Health Hazards of Alpha Particles

In general, external alpha radiation does not pose a health risk, since alpha particles can only travel distances of a few centimeters.

In this way, alpha particles are absorbed by the gases present in just a few centimeters of air or by the thin outer layer of dead skin of a person, thus preventing them from posing any risk to human health.

However, alpha particles are very dangerous to health if they are ingested or inhaled.

This is so because, even though they have little penetrating power, their impact is very large, since they are the heaviest atomic particles emitted by a radioactive source.

Applications

Alpha particles have different applications. Some of the most important are the following:

- Cancer treatment.

- Elimination of static electricity in industrial applications.

- Use in smoke detectors.

- Fuel source for satellites and spacecraft.

- Power source for pacemakers.

- Power source for remote sensor stations.

- Power source for seismic and oceanographic devices.

As can be seen, a very common use of alpha particles is as a source of energy for different applications.

Furthermore, one of the main applications of alpha particles today is as projectiles in nuclear research.

First, alpha particles are produced by ionization (that is, separating electrons from helium atoms). Later these alpha particles are accelerated to high energies.

References

1. Alpha particle (nd). In Wikipedia. Retrieved on April 17, 2018, from en.wikipedia.org.
2. Alpha decay (nd). In Wikipedia. Retrieved on April 17, 2018, from en.wikipedia.org.
3. Eisberg, Robert Resnick, Robert (1994). Quantum Physics: Atoms, Molecules, Solids, Nuclei, and Particles. Mexico DF: Limusa.
4. Tipler, Paul; Llewellyn, Ralph (2002). Modern Physics (4th ed.). WH Freeman.
5. Krane, Kenneth S. (1988). Introductory Nuclear Physics. John Wiley & Sons.
6. Eisberg, Robert Resnick, Robert (1994). Quantum Physics: Atoms, Molecules, Solids, Nuclei, and Particles. Mexico DF: Limusa.