The selectivity and efficiency of the covalent attachment of pyrene molecules to chains of polyethylene (PE) films by various forms of ionizing radiation (neutrons, electrons, protons, and (x particles) have been examined while varying several aspects of the reactions. The results are compared with those from irradiations by >300 nm (<4.1 eV) photons. For each type of ionizing radiation, selectivity and attachment efficiency (G) increase with decreasing particle dose. Bombardment by protons, alpha particles, and electrons produces significant amounts of pyrene molecules attached at two positions, whereas comparable doses of >300 nm (<4.1 eV) photons yield monosubstituted pyrenes only. Higher doses of photons result in attached species that are not pyrenyl in nature. Selectivity is independent of particle kinetic energy in the 3.0-7.0 MeV range for alpha particles and in the 1.0-4.5 MeV range for protons. Bombardment by <2.0> MeV neutrons is the least efficient of the ionizing radiation sources explored. Selectivity of attachment is independent of PE crystallinity and so is efficiency when protons or alpha particles are the radiation source. Significant cross-linking and scission of PE chains accompanies the bombardments at higher doses. The nature of the transformation of particle kinetic energy to potential energy and eventually to work as a function of depth of penetration is explored by analyzing individual pyrene-doped PE films that were bombarded in stacks. They indicate that both the selectivity and efficiency of attachment correlate in different ways with the linear transfer of energy to a film. Where direct comparisons are possible, the differing forms of ionizing radiation appear to interact with the polymer matrixes in a somewhat similar manner. However, there are important, subtle differences as well and they are indicated.