Properties of ion track in polystyrene irradiated with high energy 56Fe ions

Polystyrene (PS) films were irradiated with 1.157 GeV 56Fe ions at room temperature to fluences of 1 × 1012 ions/cm2 at various electronic energy loss values. Ultraviolet–visible (UV–vis) spectra were measured to investigate the optical properties of the irradiated materials. Optical constants of virgin and irradiated PS were evaluated in the UV–vis frequence range through fitting of UV–vis spectra with the multi-Lorentz model. Furthermore, effective medium theory was applied to evaluate the optical constants of materials in the ion track area. It is found that the refractive index of ion track material decreased significantly in the ultraviolet–visible range whereas its extinction coefficient increased. Gas atom release and carbon atom conglomerating are believed to be the reason. The extracted track radius and its variation with electronic energy loss values are in good agreement with earlier studies.