Decomposition of the absorption spectrum of irradiated EBT-XD films with 6 MV photon in lorentzian functions

The introduction of radiochromic films has solved some of the problems associated with conventional 2D radiation detectors. EBT-XD radiochromic film was introduced as the next generation of EBT, EBT2 and EBT3 films while maintaining the composition of the active layer based on polydiacetylene. Precise knowledge of the absorption spectra of these films can help develop optical densitometers more suitable for clinical use. The objective of this work is to present an analysis of the net absorption spectra of EBT-XD radiochromic films by means of Lorentz decomposition. The net absorption spectra of the EBT-XD films showed the two characteristic absorption bands of the active layer component, based on polydiacetylene (PCDA), centered at 636±1 nm and 585±1 nm, also reported for the EBT models, EBT2 and EBT3. The band reported at 560±1 nm was also observed. Furthermore, the net absorption spectra of the EBT-XD films show a series of bands for the wavelength range 400 to 540 nm. These bands have already been reported for the EBT3 film model, the authors attributed this behavior to a possible interference effect characteristic of a Fabri-Perot cavity formed by the symmetric structure of the films. The Lorentz decomposition of the net absorption spectrum of the EBT-XD films showed the presence of 12 Lorentz functions, unlike the absorption spectrum of the EBT and EBT2 radiochromic film models, which decomposes into 8 Lorentz functions. Lorentz functions are commonly used when modeling optical transitions between electron bands.