UV-Vis spectroscopic and chemical etching studies of CR-39 (PADC) exposed to ultraviolet radiation

UV-Vis spectroscopic and chemical etching studies of CR-39 detector exposed separately to UV radiation of wavelengths 365 nm, and 254 nm at different exposure times were investigated. For CR-39 detector exposed to ultraviolet radiation of wavelength 365 nm, there was no significant changes either in the bulk etching rate V-B or UV-Vis spectra. UV-Vis spectra of CR-39 detector exposed to ultraviolet of wavelength 254 nm) showed a blue and red shift. The direct and indirect band gaps of CR-39 polymer were determined. It was found that the indirect and direct band gap decrease with the increase of the exposure time. The width of the tail of localized states in the band energy gap Delta E was obtained using Urbach's formula. The Urbach's energy Delta E increases by the increase of exposure time. Applying the proposed formula to determine the bulk etch rate of CR-39 exposed to short-wavelength ultraviolet leads to the modification of bulk etch rate by a factor ranging from 18\% to 86\% after 0.5 hour of etching time. The dependence of CR-39 response on the incident angle was investigated. It is found that the response is decreasing by the increase of incident angle and therefore it should be considered when using CR-39 as UV dosimeter.