Effect of γ-ray irradiation on structure formation and optical constants of thermally evaporated rhodamine B thin films

Rhodamine B (RhB) is polycrystalline in powder form; it becomes nanocrystalline in thermally evaporated films. Gamma-rays induce nanocrystalline to amorphous transformation of RhB films. The optical constants are independent of film thickness. The type of electronic transition for as-deposited and gamma-ray irradiated RhB film is indirect allowed one. The onset and optical energy gap for as-deposited films are 2 and 3.45 eV, respectively. Exposure to different γ-ray doses did not change the transmittance and reflectance behavior of RhB films. γ-ray irradiation decreases onset and optical energy gap, refractive index and dispersion parameters and increase extinction coefficient, oscillator and electric dipole strengths.