Abstract
Samples of CR-39 polyallydiglycol polymer after irradiation with Am-241 alpha particles were exposed to Nd: YAG (UV) laser pulses with different wavelengths (lambda=355 nm and lambda=266nm with same repetition rate of 10Hz and pulse duration of 8 nano seconds). In order to investigate the changes occurred in the original morphology of the latent tracks, samples were etched in 6M NaOH at 70 degrees C for different periods. Our results indicate significant changes in track sizes, shapes and chain-like structures. The enlargement of average track diameters leading to overlapping of tracks as a function of exposure time and energy was observed. The increase in circular annealed central area around the laser pulses and disappearance of tracks from this area as a function of energy was observed. The results can best be explained by considering that absorption of UV photons by organic molecules which give rise to electronic excitation. It is believed that when a polymer is excited with photons of higher energy, the decomposition and ablation is predominantly photochemical, being caused by the excitation and dissociation of bonds. The result is scission of bonds and the production of a large number of small volatile fragments during the absorption of the UV radiation. Surface morphology and microstructure changes observed are wavelength and exposure time dependent.