Dynamics of ultraviolet laser ablation of polymer surfaces.

Abstract

The dynamics of the ablation process have been analyzed as a series of elementary chemical steps. It has been suggested that chromophores that are doubly or multiply excited play an important part in UV ablation, particularly at wavelengths longer than 193 nm, because decomposition from upper electronic excited states is not only fast (on the time scale of molecular vibrations) but proceeds with an efficiency close to 100% of the centers that are excited. Such reactions yield small molecules as products. For nearly all polymers, whether or not they absorb strongly, the ablation threshold falls within narrow limits. The uncertainty is larger in the strongly absorbing polymers because of experimental problems.