The response characterization of Gafchromic TM EBT2 film to ultraviolet radiation of short wavelength (UVC)

Abstract

The GafchromicTM EBT2 was assessed for changes in its irradiated optical properties with ultraviolet radiation of short-wavelength (UVC) at 254 nm for different durations. The characteristic absorbance peak of the EBT2 film at 633 nm is correlated to the orientation angle as a sinusoidal function. Therefore, all samples must be orientated to 40° or 220° to give their maximum absorbance. The variation in Urbach’s energy and indirect and direct optical band gaps to (UVC) was determined by the UV-vis spectrum. The results reveal that as the UVC exposure time increases, EBT2 absorbance increases at all wavelengths, with the largest increases exceeding 500 nm. Furthermore, the absorbance which is a monotonic function of the exposure time up to 14 h occurs at (582 2) nm and (632 2) nm and three colors: red (650 nm), green (510 nm), and blue (475 nm). Such absorbance was broadened because of both red-and-blue shift causes absorption increases significantly. Meanwhile, the maximum sensitivity is perceived at (581 2) nm. Likewise, there is a slight significant increase in the direct and indirect energy band gaps with the exposure time up to 14 h. Thereafter, the values declined with the increase in the exposure time. By contrast, Urbach’s energy decreased with exposure time up to 14 h and then increased considerably with UVC exposure time. Finally, we speculate that these findings were attributed to the polymerization of diacetylene monomer to form polydiacetylene for short exposure periods, after which it saturates.