Drastic decrease of carbonyl group after the loss of ether in PADC exposed to 222 nm UV photons

We aim to elucidate the chemical damage structure in poly(allyl diglycol carbonate), PADC, exposed to UV photons with a wavelength of 222 nm using FT-IR spectrometric method. The number density of carbonyl (C˭O) in PADC, which composes carbonate ester, is hardly affected by the UV photons below the critical fluence of 3.0 × 1019 photons/cm2. The number density of carbonyl decreases only above the critical fluence, while those of ether and C-O-C in carbonate ester are monotonically cleaved. These findings corroborate the previous result using 28 MeV electron beams, in which the carbonate ester is lost only above the critical fluence of 1.6 × 1015 electrons/cm2, where the overlapping of electron tracks becomes significant. We extend the conventional track overlapping model to clarify the spatial distribution of point-like defects after the UV exposure. The discrete damage is seen at the critical condition, based on the extended track overlapping model.