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Journal of Adhesion Science and Technology 

 5

Figure 3. The dependence of (ΑhΝ)0.5 on photon energy (hΝ) for pristine- and gamma-irradiated PC/
PBT polymer.

Figure 4. The optical band gap energy (Eg) and number of carbon atoms (N) as a function of gamma
doses for PC/PBT polymer.

decreases form 5.0  eV for the pristine sample to 4.4  eV for irradiated sample with the
highest gamma dose for direct transition. While in case of indirect transition, the optical
band gap decreases form 4.4 eV for the pristine sample to 3.5 eV for irradiated sample with
the highest gamma dose. These decreases may be attributed to excitation of non-bonding
electrons caused by the formation of defects into the conduction band with their subsequent
on localized states.[25] The creation of free radicals, which cause an increase in the carriers
on localized states, lead to decrease in the transition probabilities into the extended states
that give rise to additional absorption and hence improve in the electrical conductivity of
the irradiated polymers.[36,37] Furthermore, a significant dependence of optical band gap