1.2.1 Ionizing radiation takes a few forms

Alpha, beta, neutron particles, gamma rays and X-rays are each caused by unstable atoms, either through the overabundance of vitality or mass (or both of them).

To reach a steady state, they must discharge that additional vitality or mass within the frame of radiation.

Alpha particles (α particle): positive charged particles (+2), which are released in the radioactive decay of some nuclei. An alpha is a particle which is emitted from the nucleus of an atom, which consists of (+2) protons and (2) neutrons with mass number (4) (Helium atom). It is strong ionizing with low penetration power and short range.

Beta particles (β+ or β-): They are particles with electric charge ((+) or ()) emitted from the nucleus during radioactive decay. They take the form of either an electron or a positron (a particle with the size and mass of an electron, but with a positive charge).

• Electrons or positrons have small mass and variable energy. Electrons are formed when a neutron transforms into a proton and an electron.

Gamma rays: are different from alpha or beta rays, because they do not contain any particles, as they are used in electromagnetic radiation. Instead, they consist of a photon of energy, which is released from an unstable nucleus of an atom.

Isomeric transition: It occurs when the excited atomic nucleus changes from a higher to a lower state of the energy by emitting gamma ray.

Internal conversion electron: This process occurs when the gamma rays are not released sometimes, so they provide their exceed energy to the electron in the atomic orbit; this process usually happens to the nearest nucleus (as shown in Figure 3).

X-rays: They are similar to gamma radiation; the only one primary difference is that they originate from the electron shell. This is generally caused by energy

• If the energy of electromagnetic waves is high, the frequency will be high with short wavelength such as those of gamma rays or heavy particles (beta and

Nonionizing radiation refers to the inability of ionizing materials because of their lower energy, Such as ultraviolet radiation, visible light, infrared photons,

• If the energy of electromagnetic waves is low, the frequency will be low with

• Not enough energy to pull electron from orbit, but the electron can exit [3].

long wavelength such as those of radio waves and microwaves.

• Enough high energy to pull electron from orbit [2].

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microwaves and radio waves (as shown in Figure 2).

Ionizing radiation is classified into two types:

The schematic representation of the different regions of the electromagnetic spectrum.

1.2 Classification of ionizing radiation

i. Directly ionizing radiation

alpha).

Classification of radiations.

Figure 1.

Figure 2.

24

1.1.2 Nonionizing radiation

#### Figure 3.

Emission of an auger electron as an alternative to X-ray emission. No X-ray is emitted.

#### Figure 4.

How the emission of the characteristics of X-ray occurs when the orbital electrons move from an outer shell so as to fill in the inner shell vacancy.

changes in an electron, such as moving from a higher energy level to a lower one. This causes the excess energy to be released. X-rays are called characteristic X-ray. It (X-ray) has longer wavelength and possess (usually) lower energy than gamma radiation, as well. The emission of high-energy waves came from the electron of an atom (as shown in Figure 4).

The neutron - Proton ratio shows that if the number of protons increase, the number of neutrons must increase even more for stability. This process is shown

For proton numbers (Z) up to 20, N = Z could be a straight line. For all nuclei with Z > 20, stable nuclei have less protons than neutrons; the line bends upwards. Unsteady nuclei over the soundness bend are called neutron-

Radioactive decay is the process by which the unstable nucleus tries to change into a more stable form. As, it is the process in which the transformation will take

in Figure 5.

Figure 5.

rich [1].

2.1 Radioactive decay

Basic Modes of Radioactive Decay

DOI: http://dx.doi.org/10.5772/intechopen.85502

2.2 Types of decays

1.Beta decay

2.Gamma decay

5.Alpha decay

27

3.Electron capture

4.The positron decay

place depending on the composition of the nucleus.

A neutron particle is an uncharged element particle with a mass that is slightly greater than that of the proton, and it is found in the nucleus. It is usually released because of spontaneous or induced nuclear fission.

### 2. Radioactive decay (nuclear decay)

Radioactive decay is a process in which an unstable nucleus transforms into a more stable one by releasing particles or photons. In addition, it results in the conversion of mass into energy.

In some decay modes, electron mass is converted into energy as well. The total mass-energy conversion amount is called the transition energy. Most of this energy is imparted as kinetic energy to released particles or is converted to photons with a small portion as kinetic energy.

In a few decay modes, electron mass is changed into vitality as well. The full mass-energy transformation sum is called the transition energy. Most of this energy is imparted as active energy to discharged particles or is changed over to photons with a little portion as kinetic energy [4].

#### Figure 5.

changes in an electron, such as moving from a higher energy level to a lower one. This causes the excess energy to be released. X-rays are called characteristic X-ray. It (X-ray) has longer wavelength and possess (usually) lower energy than gamma radiation, as well. The emission of high-energy waves came from the electron of an

How the emission of the characteristics of X-ray occurs when the orbital electrons move from an outer shell so as

Emission of an auger electron as an alternative to X-ray emission. No X-ray is emitted.

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A neutron particle is an uncharged element particle with a mass that is slightly greater than that of the proton, and it is found in the nucleus. It is usually released

Radioactive decay is a process in which an unstable nucleus transforms into a more stable one by releasing particles or photons. In addition, it results in the

In some decay modes, electron mass is converted into energy as well. The total mass-energy conversion amount is called the transition energy. Most of this energy is imparted as kinetic energy to released particles or is converted to photons with a

In a few decay modes, electron mass is changed into vitality as well. The full mass-energy transformation sum is called the transition energy. Most of this energy is imparted as active energy to discharged particles or is changed over to photons

atom (as shown in Figure 4).

to fill in the inner shell vacancy.

Figure 3.

Figure 4.

conversion of mass into energy.

small portion as kinetic energy.

26

with a little portion as kinetic energy [4].

because of spontaneous or induced nuclear fission.

2. Radioactive decay (nuclear decay)

For proton numbers (Z) up to 20, N = Z could be a straight line. For all nuclei with Z > 20, stable nuclei have less protons than neutrons; the line bends upwards. Unsteady nuclei over the soundness bend are called neutronrich [1].

The neutron - Proton ratio shows that if the number of protons increase, the number of neutrons must increase even more for stability. This process is shown in Figure 5.

#### 2.1 Radioactive decay

Radioactive decay is the process by which the unstable nucleus tries to change into a more stable form. As, it is the process in which the transformation will take place depending on the composition of the nucleus.

#### 2.2 Types of decays


#### 2.2.1 Beta decay

Beta decay or (β� decay) is a process in which the neutron in the nucleus is essentially transformed into a proton and electron:

$$\mathbf{n} \rightarrow \mathbf{p} + \boldsymbol{\upbeta}^- + \mathbf{v} + \mathbf{energy}$$

Beta decay is also the decay of one of the neutrons to a proton via the weak interaction:

$$\,\_{Z}^{A}\mathbf{X} \stackrel{\beta^{-A}}{\to} \mathbf{Y}^{\mathbf{Z}+1}$$

The electron is called β� particle (υ), meanwhile the neutrino is a particle that has no mass or electrical charge. It does not virtually undergo interactions with matter and therefore is essentially undetectable.

In internal pair production, the excess energy is converted within the electromagnetic field of a nucleus into an electron and a positron that are released together. Internal conversion always accompanies the predominant process of

Internal pair production needs the excess energy of the unstable nucleus to be at least equivalent to the combined masses of an electron and a positron (as shown

Schematic representation of internal conversion involving a K shell electron. Unstable nucleus transfers its energy

The daughter of radioactive parent may be formed in a long-lived metastable (isomeric state) as opposed to an excited state. The decay of the metastable (iso-

Isomeric transition: a nuclear process in which a nucleus has abundant energy

In many nuclides, isomeric transitions produce gamma photons and internal conversion electrons. When an electron is removed from the atom by internal conversion, a vacancy is created. All transitions are usually followed by either

The energized atomic state taking after the emission of a beta particle may be nearly steady, and the nucleus may be able to remain in this state for minutes,

The isomer (no change of the number of proton or neutron) works as a separate radioactive material, which is decaying exponentially with the emission of a gamma

Schematic representation of mutual annihilation reaction between a positron (β+) and an ordinary electron. A

following the emanation of an alpha molecule or a beta molecule and in turn discharges energy without a change in its number of protons or neutrons. Isomeric moves can occur through the emission of a gamma ray or through the process called

meric state) by the emission of a γ-ray is called isomeric transition.

hours, or even days, sometimes recently discharging a gamma ray.

pair of 0.511 MeV annihilation photons is released "back to back" at 180° to each other.

gamma or internal conversion electron emission.

gamma emission.

"internal conversion."

ray only [5].

Figure 8.

29

2.2.2.1 Isomeric transition conversion

to an orbital electron to release a converted electron.

Basic Modes of Radioactive Decay

DOI: http://dx.doi.org/10.5772/intechopen.85502

in Figure 8).

Figure 7.

The energy released in β�decay is shared between β�particle and neutrino (υ). This sharing of energy is more or less random from one decay to the next. As shown in Figure 6, the plot displays the distribution of β� particle energy. It is also noticed that beta particles are not monoenergetic for a particular radionuclide, but they are released at varying energy levels over a continuous range (spectrum). The average energy of beta emission can be estimated as one-third of the maximum energy of emission: Eavg = 1/3Emax (as shown in Figure 6) [1].

#### 2.2.2 Gamma decay

It is a mechanism for an excited nucleus to release energy. Emanation could be a sort of radioactivity in which a few unsteady nuclear nuclei disseminate excess energy by an unconstrained electromagnetic radiation.

Within the most common form of gamma decay, which is called gamma emission, gamma rays (photons or bundles of electromagnetic vitality, of highly short wavelength) are radiated.

Gamma rays are electromagnetic radiation (high-energy photons) with an extreme frequency and a high energy. They are created by the decay of nuclei as they travel from a high-energy state to a lower state; this process is called "gamma decay." Most of atomic responses are accompanied by gamma emission.

Gamma decay also includes two other electromagnetic processes: internal conversion and pair production.

Internal conversion (IC) is a process in which the excess energy of the nucleus is directly transferred to one of its own orbital electrons which is ejected instead of the ray. In this case, the ejected electron is called a conversion electron (as shown in Figure 7).

Figure 6. The distribution or spectrum for β� particle.

Basic Modes of Radioactive Decay DOI: http://dx.doi.org/10.5772/intechopen.85502

#### Figure 7.

2.2.1 Beta decay

interaction:

2.2.2 Gamma decay

wavelength) are radiated.

conversion and pair production.

The distribution or spectrum for β� particle.

in Figure 7).

Figure 6.

28

Beta decay or (β� decay) is a process in which the neutron in the nucleus is

n ! p þ β� þ υ þ energy

Beta decay is also the decay of one of the neutrons to a proton via the weak

The electron is called β� particle (υ), meanwhile the neutrino is a particle that has no mass or electrical charge. It does not virtually undergo interactions with

The energy released in β�decay is shared between β�particle and neutrino (υ). This sharing of energy is more or less random from one decay to the next. As shown in Figure 6, the plot displays the distribution of β� particle energy. It is also noticed that beta particles are not monoenergetic for a particular radionuclide, but they are released at varying energy levels over a continuous range (spectrum). The average energy of beta emission can be estimated as one-third of the maximum energy of

It is a mechanism for an excited nucleus to release energy. Emanation could be a

Within the most common form of gamma decay, which is called gamma emission, gamma rays (photons or bundles of electromagnetic vitality, of highly short

Gamma rays are electromagnetic radiation (high-energy photons) with an extreme frequency and a high energy. They are created by the decay of nuclei as they travel from a high-energy state to a lower state; this process is called "gamma

Gamma decay also includes two other electromagnetic processes: internal

Internal conversion (IC) is a process in which the excess energy of the nucleus is directly transferred to one of its own orbital electrons which is ejected instead of the ray. In this case, the ejected electron is called a conversion electron (as shown

decay." Most of atomic responses are accompanied by gamma emission.

sort of radioactivity in which a few unsteady nuclear nuclei disseminate excess

A ZX ! β�<sup>A</sup> Zþ1 YZþ<sup>1</sup>

essentially transformed into a proton and electron:

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matter and therefore is essentially undetectable.

emission: Eavg = 1/3Emax (as shown in Figure 6) [1].

energy by an unconstrained electromagnetic radiation.

Schematic representation of internal conversion involving a K shell electron. Unstable nucleus transfers its energy to an orbital electron to release a converted electron.

In internal pair production, the excess energy is converted within the electromagnetic field of a nucleus into an electron and a positron that are released together. Internal conversion always accompanies the predominant process of gamma emission.

Internal pair production needs the excess energy of the unstable nucleus to be at least equivalent to the combined masses of an electron and a positron (as shown in Figure 8).

#### 2.2.2.1 Isomeric transition conversion

The daughter of radioactive parent may be formed in a long-lived metastable (isomeric state) as opposed to an excited state. The decay of the metastable (isomeric state) by the emission of a γ-ray is called isomeric transition.

Isomeric transition: a nuclear process in which a nucleus has abundant energy following the emanation of an alpha molecule or a beta molecule and in turn discharges energy without a change in its number of protons or neutrons. Isomeric moves can occur through the emission of a gamma ray or through the process called "internal conversion."

In many nuclides, isomeric transitions produce gamma photons and internal conversion electrons. When an electron is removed from the atom by internal conversion, a vacancy is created. All transitions are usually followed by either gamma or internal conversion electron emission.

The energized atomic state taking after the emission of a beta particle may be nearly steady, and the nucleus may be able to remain in this state for minutes, hours, or even days, sometimes recently discharging a gamma ray.

The isomer (no change of the number of proton or neutron) works as a separate radioactive material, which is decaying exponentially with the emission of a gamma ray only [5].

#### Figure 8.

Schematic representation of mutual annihilation reaction between a positron (β+) and an ordinary electron. A pair of 0.511 MeV annihilation photons is released "back to back" at 180° to each other.

#### 2.2.3 Electron capture

Electron capture decay: it is an inverted β�decay, whereas an orbital electron is captured by the nucleus and combines with a proton to form a neutron:

$$\mathbf{p}^+ + \mathbf{e}^- \to \mathbf{n} + \mathbf{v} + \text{energy} \tag{3}$$

where A = activity; N = the number of decay nuclei in the sample; λ = decay

where A is the activity of radionuclide at a given time t; A0 is the activity of

). Activity can be determined by direct measurement.

Half-life: It is the amount of time taken for the given quantity so as to be decreased to half of its initial value. As shown in Figure 10, the term is most commonly used in relation to atoms undergoing radioactive decay, but it can be used to describe other types of decay, whether exponential or not. One of the most

where T½ is the half-life of radionuclides; ln2 = 0.693 is the base of natural



The decay constant (λ) is the probability that a nucleus will decay per second, so

decay is characterized by disappearance of a constant function of activity or

) is an exponential function of time (t). Exponential

<sup>A</sup> <sup>¼</sup> A0 <sup>e</sup>–λ<sup>t</sup> (6)

T½ ¼ Ln2=λ (7)

constant.

its unit is (s�<sup>1</sup>

2. SI unit

Figure 10.

31

2.2.6 Units of radioactivity

1.Conversion unit

The decay factor (e�λ<sup>t</sup>

Basic Modes of Radioactive Decay

DOI: http://dx.doi.org/10.5772/intechopen.85502

number of atoms prevented per unit time interval:

radionuclide at time t = 0; decay constant (λ).

1 Ci = 3.7 � <sup>10</sup><sup>10</sup> dps = 37 GBq. 1 mCi = 3.7 � <sup>10</sup><sup>7</sup> dps = 37 MBq. <sup>1</sup> <sup>μ</sup>Ci = 3.7 � <sup>10</sup> <sup>4</sup> dps = 37 kBq.

well-known applications of half-life is:

logarithms; λ is decay constant of radionuclides.

The time required for it to decay the number of radioactive nuclei to 50% of the (NO).

In other words, we can say that the electron capture is a process, in which a parent nucleus captures one of its orbital electrons and releases a neutrino. This neutrino is emitted from the nucleus and carries away some of the transitions energy. The remaining energy appears in the form of characteristic X-rays and Auger electrons, which are emitted by daughter product, whereas the resulting orbital electron vacancy is filled (as shown in Figure 9).
