Polystyrene films were irradiated with 3MeV silicon ions ranging from 1×10 12ions/cm 2 to 3×10 14ions/cm 2 at room temperature. Fourier-transform infrared spectra

reflection spectra and ultraviolet/visible transmission spectra were measured to investigate the radiation induced chemical modifications of the material. It was found that the material underwent significant degradation at fluences higher than 3×10 13ions/cm 2

corresponding to an average energy deposition of about 45MGy. Most of the functional groups including the phenyl ring were destroyed at high fluence. Simultaneously the energy gap of the material decreased with increasing fluence. At fluences of 1×10 14ions/cm 2 and 3×10 14ions/cm 2

the energy gap reduced from about 2.7eV to 1.85eV and 1.2eV

respectively. It is concluded that the irradiated film is transformed gradually into hydrogenated amorphous carbon at high fluence.