Yields of CO2 formation and scissions at ether bonds along nuclear tracks in CR-39

Yields of CO2 gas formation and the scissions at ether bonds have been determined along ion tracks in CR-39 plastics. Thin CR-39 films with 15μm thickness were irradiated by 130 MeV C-13 ions at 45∘ incidence up to 1013ions/cm2, and then IR spectra were obtained without removing the samples from the vacuum chamber. The absorption band for CO2 was observed clearly around 2338cm-1, whose absorbance increased proportional to the fluence up to 3×1012 ions/cm2 and then saturated. Using a mole absorption coefficient for gaseous CO2, the yield along the track was determined to be 7200CO2molecules/μm. This means that the G-value of CO2 formation in CR-39 was about 3.6 molecules/100 eV. The scission yield of ether bonds was found to be 11,000 scissions/μm. This corresponds to a G-value of about 5.5 scissions/100 eV. These values suggest that the parts between the two carbonate ester bonds in each repeat unit of CR-39 can be segmented into two CO2 and other small molecules along the nuclear tracks.