title: Influence of gamma ray irradiation and annealing temperature on the optical constants and spectral dispersion parameters of metal-free and zinc tetraphenylporphyrin thin films: A comparative study.
abstract: In this work, we report on the effect of γ-ray irradiation and annealing temperature on the optical properties of metal-free tetraphenylporphyrin, H2TPP, and zinc tetraphenylporphyrin, ZnTPP, thin films. Thin films of H2TPP and ZnTPP were successfully prepared by the thermal evaporation technique. The optical properties of H2TPP and ZnTPP films were investigated using spectrophotometric measurements of the transmittance and reflectance at normal incidence of light in the wavelength range from 200 to 2500 nm. The absorption spectra of H2TPP showed four absorption bands, namely the Q, B, N and M bands. The effect of inserting Zn atom into the cavity of porphyrin macrocycle in ZnTPP molecule distorted the Q and B bands, reduced the width of absorption region and influenced the optical constants and dispersion parameters. In all conditions, the type of electron transition is indirect allowed transition. Anomalous dispersion is observed in the absorption region but normal dispersion occurs in the transparent region of spectra. We adopted multi-oscillator model and the single oscillator model to interpret the anomalous and normal dispersion, respectively. We have found that the annealing temperature has mostly the opposite effect of γ-ray irradiation on absorption and dispersion characteristics of these films.
authors.affiliation: Department of Physics, Faculty of Science at New Damietta, 34517 New Damietta, Egypt.
authors.forename: H M
authors.initials: HM
authors.lastname: Zeyada
authors.affiliation: Department of Physics, Faculty of Science at New Damietta, 34517 New Damietta, Egypt; Department of Physics, Faculty of Applied Medical Sciences at Turabah, Taif University, 21995, Saudi Arabia; Department of Physics, Damietta Cancer Institute, Damietta, Egypt. Electronic address: m_makhlof@hotmail.com.
authors.forename: M M
authors.initials: MM
authors.lastname: Makhlouf
authors.affiliation: Department of Physics, Faculty of Education, Ain Shams University, Cairo 11757, Egypt.
authors.forename: M M
authors.initials: MM
authors.lastname: El-Nahass
keywords: Annealing temperature; Optical properties; Porphyrins; Thin films; γ-Ray irradiation