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Radiative stopping power (S_{rad}) is due to radiative interactions and is mostly based on Bremsstrahlung production alone. Different from collision (ionization) stopping power, only light charged particles
(electrons and positrons) experience appreciable energy losses through
these interactions. This type of radiative stopping power results from charged particle Coulomb interaction with nuclei of the absorber. Energy spent in radiative collisions is carried away from the chargedparticle track by the photons.
The radiative stopping power can be evaluated easily by the mass radiative stopping power S_{rad} (in MeV · cm^{2}/g), which is one type of the mass stopping powers. S_{rad} is given by,
 [4431a]
where,
N_{a}  The number of atoms per unit mass (N_{a} = N/m)
σ_{rad}  The total cross section for bremsstrahlung production
E_{i}  The initial total energy of the light charged particle, given by E_{i} = E_{Ki} +
m_{e}c^{2}
E_{Ki}  The initial kinetic energy of the light charged particle
Inserting σ_{rad} for nonrelativistic particles S_{rad} can by rewritten by,
 [4431b]
where B_{rad} is a slowly varying function of Z and E_{i}. The mass radiative stopping power S_{rad} is proportional to (N_{A}Z^{2}/A), that indicates a proportionality with the atomic number Z of the matter and the initial total energy E_{i} of the light
charged particle as shown in Figure 4431.
Figure 4431. Mass radiative and collision stopping powers for electrons in water (H_{2}O), aluminum (Al)
and lead (Pb)
shown with red and green curves, respectively, against the electron kinetic energy. Adapted from NIST.
