Abstract

Recent investigations of 193-nm ArF-excimer-laser ablation of collagen films have revealed transient absorption increases in hydrated targets at ablative fluences.¹ Two pathways have been proposed to account for dynamic absorption increases: secondary structure denaturation of collagen in the tissue target and absorption by free radicals generated by photolytic-peptide-bond cleavage. We propose a novel third pathway: a dynamic shift in the 193-nm absorption coefficient of water during the excimer-laser pulse. The room-temperature absorption spectrum of water places 193 nm adjacent to a large absorption edge rising to over 60 000 cm⁻¹ as one approaches 160 nm.²

© 1995 Optical Society of America