Spectral analysis of the EBT3 radiochromic film irradiated with 6 MV X-ray radiation

• The EBT3 film exhibit two absorption bands centered at around 636 and 585 nm.
• Absorption spectra of the EBT3 films was decomposed into Lorentzian functions.
• The symmetrical structure of the EBT3 film behaves like a Fabry-Perot cavity.

The EBT3 radiochromic film was introduced as the next generation of EBT and EBT2 films, maintaining the composition of the active layer. X-ray radiation produces a change in its visible light absorption spectrum and optical properties being granted make the films suitable for dosimetric applications. The goal of this study is to present results of absorption spectra measurements for the EBT3 radiochromic film exposed to 6 MV X-ray radiation in the dose range from 0 to 50 Gy. Results showed that the spectrum of the EBT3 radiochromic has an intense band centered at around 636 nm and a less intense centered at around 585 nm. Spectral analysis show that in addition to the two main absorption bands, the absorption spectrum in the spectral range from 400 to 700 nm contains nine more absorption bands. Because to the symmetrical structure of the EBT3 radiochromic film, we assume that the additional absorption bands in the spectral range 400–540 nm are due to an interference pattern that is characteristic of a Fabry-Perot cavity.