PENELOPE 2003 - OECD Nuclear Energy Agency

Chapter 2
Photon interactions
In this chapter, we consider the interactions of unpolarized photons of energy E with
atoms of atomic number Z. We limit our considerations to the energy range from 100 eV
up to 1 GeV, where the dominant interaction processes are coherent (Rayleigh) scattering,
incoherent (Compton) scattering, the photoelectric effect and electron-positron
pair production. Other interactions, such as photonuclear absorption, occur with much
smaller probability and can be disregarded for most practical purposes (see e.g. Hubbell
et al., 1980).
E
E e
= E−U i
E
θ
E
θ e
Fluorescence
E
Rayleigh scattering
Ph otoe l e ctric ab s orption
E
E'
+
E
θ
θ +
θ e θ −
E e
E −
C om pton s catte ring
Pair production
Figure 2.1: Basic interactions of photons with matter.