Chapter 3 - Properties of radiations emitted from radionuclides

Summary

Tools for applications

This chapter will introduce radionuclides and the emitted radiations as tools for applications. We shall begin with the well known α, β and γ radiations followed by a few characteristics of extranuclear electrons and X rays. Additional comments about neutrons (see Section 1.3.6), will follow in Section 5.4.4.

Properties of alpha particles

The nature and origin of alpha particles

Alpha particles are here called primary radiations because their emission is the first evidence of nuclear disintegrations which turn parent atoms into daughter atoms belonging to a different chemical element. Alpha particles are emitted either as a single branch, i.e. all with the same energy, or as several branches each with its own energy. A typical case is the α particle decay of americium-241. Close to 13% of the decays occur at an α particle energy of 5.44 MeV and close to 85% at 5.48 MeV, leaving three minor branches each with its own energy, overall exactly one α particle emitted per decay.

Properties of a particles were summarised in Table 1.2. With Z = 2 and A=4, α particles are physically identical to the nuclei of helium atoms. As calculated by Rutherford (Section 1.2) the diameter of α particles is about 10⁻¹⁴ m, or some 10⁴ times smaller than the 10⁻¹⁰ m atomic diameters.